How to Use an Old Laptop as a Second Monitor (Windows)

An old laptop may be too slow to use as your main computer but still have a perfectly good screen.

That makes the obvious question: can you turn it into a second monitor?

Yes, in many Windows setups you can.

The easiest built-in method uses Windows Wireless Display and Miracast. Your main PC sends an extended desktop to the old laptop wirelessly, allowing you to move browser windows, documents, chats, or other apps onto its screen.

There is one common misunderstanding to clear up first, though.

Plugging an HDMI cable between two ordinary laptops usually will not work.

Quick answer

To use an old Windows laptop as a second monitor, install the Wireless Display optional feature on the old laptop, open the Wireless Display app, then press Windows + K on your main Windows PC and connect to it.

Choose Extend as your display mode if you want additional desktop space rather than a copy of the main screen.

Both devices need compatible wireless-display support. Microsoft says Miracast support and Wi-Fi are required for this type of connection.

Why an HDMI cable usually does not work

This is where many people lose time.

A laptop having an HDMI port does not automatically mean it can receive video.

On most laptops, HDMI is used to send the laptop’s picture out to a monitor or TV. It is an output.

To use the laptop screen as a conventional wired monitor, the machine would need a video input designed to accept an external signal.

Most ordinary notebooks do not have that.

HP support guidance for multiple notebook models, along with Microsoft Q&A guidance on this exact use case, notes that their laptop HDMI connections are output-only.

Check your exact model if you are unsure, because rare exceptions exist.

What you need

For the built-in Windows method, you need:

• a main Windows PC
• the old Windows laptop you want to use as the display
• Windows 10 or Windows 11 on compatible devices
• Wi-Fi enabled
• Miracast/wireless projection support

On current Windows 11 systems, Microsoft uses the Wireless Display optional feature and Wireless Display app for projecting to another PC.

Step 1: Set up the old laptop

Turn on the laptop that will become your second screen.

• Open: Settings → System → Projecting to this PC

• If Windows tells you that the Wireless Display feature is not installed, open Optional features.
• Choose the option to add a feature and search for:
• Wireless Display
• Install it.
• Microsoft lists Wireless Display as the optional Windows feature required for projecting to another Windows PC.

Once installation finishes, return to the projection settings.

Step 2: Adjust projection permissions

Choose when the laptop should allow another PC to connect.

The exact wording can vary slightly by Windows version, but the goal is to make the laptop discoverable for projection.

On a personal home setup, choose settings that require your approval before another device projects to the screen.

If you see an option requiring the laptop to be plugged in before it can be discovered, decide whether that suits your setup.

Using an old laptop as a display for long periods is usually more convenient while it is connected to power anyway.

Step 3: Open Wireless Display on the old laptop

Search Windows for:

• Change block type or style
• Move Paragraph block from position 35 up to position 34
• Move Paragraph block from position 35 down to position 36
• Change alignment
• Change text alignment
• Displays more block tools
• Wireless Display
• Open the app.
• Leave it running while you move to your main computer.

On Windows 11 version 22H2 and later, Microsoft directs users to the Wireless Display app. Older supported Windows versions may instead use the Connect app.

Step 4: Connect from your main PC

On the main computer, press:

Windows + K

Windows will show compatible wireless displays nearby.

Select the name of your old laptop.

The old laptop may ask whether you want to allow the connection.

Approve it.

If a PIN appears, follow the pairing instructions shown by Windows.

After a moment, the primary computer’s desktop should appear on the old laptop.

Step 5: Change the display to Extend

You now need to tell Windows what the second screen should do.

Press: Windows + P

Choose: Extend

Microsoft defines Extend mode as spreading the desktop across multiple displays so you can move items between them.

Do not choose Duplicate if your goal is additional workspace.

Duplicate simply shows the same content on both screens.

Step 6: Arrange the displays correctly

Right-click the desktop on your main PC and open Display settings.

You should see numbered display boxes.

Drag them so their positions match the physical arrangement on your desk.

If the old laptop sits to the left of your main screen, place its display box on the left.

If it sits on the right, move it right.

This matters because Windows uses that layout to decide where the mouse goes when it reaches the edge of a screen.

Adjust scaling or resolution if text looks too small or unusually large.

What should you use the second laptop screen for?

Wireless projection is useful for secondary tasks that do not need instant response.

Good examples include:

email, messaging apps, reference documents, music controls, notes, calendars, dashboards, browser tabs, or a video you are not actively editing.

It is less suitable for fast gaming or work where even small display delays become annoying.

Wireless display introduces more latency than a normal monitor attached directly by HDMI or DisplayPort.

That is simply the trade-off for repurposing a complete laptop as a wireless screen.

What if Windows + K cannot find the laptop?

Start with the simple checks.

Make sure Wi-Fi is enabled on both computers.

Make sure the Wireless Display app is installed and running on the old laptop.

Check: Settings → System → Projecting to this PC

and confirm that projection is allowed.

Microsoft also recommends checking Miracast support, updating drivers, restarting the PCs, and removing/reconnecting the wireless display if a connection fails.

How to check whether Miracast is supported

On your main Windows PC, press Windows + K.

If Windows reports that the device does not support Miracast and must connect to an external display with a cable, the built-in wireless method may not work on that hardware.

Microsoft specifically uses Windows + K as one way to identify lack of Miracast support.

The target laptop also needs the appropriate wireless-display capability.

Very old Wi-Fi or graphics hardware can be the limiting factor even if Windows itself is installed correctly.

What if the old laptop is too old?

An old laptop does not need to be fast for this job, but it still needs to run the required software and wireless hardware reliably.

If it struggles to run Windows 10 or 11, does not support Miracast, or has unreliable Wi-Fi, the built-in method becomes less practical.

At that point, your alternatives include third-party network display software, remote desktop-style tools, or a hardware video-capture solution.

Each has trade-offs.

If you simply need a dependable second display every day, a used monitor may ultimately be easier.

Repurposing the laptop makes the most sense when you already own it and the wireless setup works with your hardware.

Can you use a capture card instead?

A USB video capture device can accept HDMI output from another computer and show it inside capture software on the laptop.

That is technically different from turning the laptop into a native monitor.

The video usually appears inside an application window rather than becoming a normal low-latency display connection.

This can be useful for viewing an external source, but it is not my first choice for a productivity-focused second-monitor setup.

For ordinary Windows-to-Windows use, try Wireless Display first.

Can you use an old laptop as a second monitor with a desktop PC?

Yes, Your main computer does not have to be another laptop.

A Windows desktop can project to the old Windows laptop in the same way, provided the required Miracast and wireless capabilities are available.

This is actually a useful setup when the desktop already has one main monitor and you want an extra screen for reference material or chat.

Can you use the laptop keyboard and touchpad too?

Windows projection can support interaction depending on the devices and projection settings.

But if your goal is simply an extra display, it is usually less confusing to control everything from the keyboard and mouse connected to the main computer.

Think of the old laptop primarily as screen space.

Will this slow down the main PC?

There is some overhead involved in encoding and transmitting the display wirelessly.

On a reasonably modern PC doing normal office or browser work, it is usually manageable.

Performance depends on your hardware, wireless connection, resolution, and what is being shown.

If the connection feels laggy, avoid placing fast-moving video or animation on the wireless display.

Static or slowly changing windows are much more forgiving.

Is an old laptop better than buying a second monitor?

For occasional use, it can be.

You already own the screen, so the setup may cost nothing.

For daily professional use, a dedicated monitor still has advantages: lower latency, easier startup, better reliability, and no second operating system running just to display an image.

The old-laptop approach is best viewed as a useful way to reuse hardware rather than a perfect replacement for a monitor.

Frequently asked questions

Can I use my old laptop as a second monitor?

Yes, many Windows laptops can receive a wireless projection from another Windows PC through Wireless Display and Miracast.

Can I connect two laptops with HDMI and use one as a monitor?

Usually not. Most laptop HDMI ports are outputs rather than inputs, so an ordinary HDMI cable cannot send another computer’s display into the laptop screen.

How do I extend my screen to another laptop?

Set up Wireless Display on the receiving laptop, connect to it from the main PC using Windows + K, then press Windows + P and choose Extend.

Why is Projecting to this PC unavailable?

The Wireless Display optional feature may not be installed, or the device may not support the required hardware. Check Optional Features first, then verify Miracast compatibility.

Does using a laptop as a second monitor need Wi-Fi?

For Microsoft’s built-in Miracast projection method, Wi-Fi needs to be enabled.

Is there delay when using a laptop as a wireless monitor?

Some latency is normal with wireless projection. It is generally more suitable for productivity windows and reference material than competitive gaming or other latency-sensitive work.

Final thoughts

If an old laptop still has a decent screen, there is little reason to leave it collecting dust before checking whether Wireless Display works.

Install the feature, open the receiving app, connect with Windows + K, and choose Extend.

The whole setup uses tools already built into compatible versions of Windows.

Just do not spend an hour swapping HDMI cables first.

That HDMI port is probably pointing the wrong way.