In this guide, I will show you how to install Windows XP on your old desktop.
To begin, click on this download link which will download an ISO installer file of Windows XP Professional. The file size is roughly 600mb.
Once it is downloaded, you will have to choose whether to burn the ISO to a CD, or write the contents to a USB. Both have their advantages and disadvantages. Burning to a CD is guaranteed to be supported on effectively all desktops, where as USB drives often do not work, but USB drives are reusable unlike traditional CD's and DVD's.
Depending on what format you choose, you will need to download one of 2 specific programs. To write to a CD or DVD, use ImgBurn, a free and lightweight disc burning tool. If you choose to use a USB, you will need to download the tool WinSetupFromUSB, which is also fully free.
Once either tool is downloaded and installed, you will need to write the contents of the ISO file to the desired medium. With ImgBurn it's simple, just click the "Write ISO to disc" button, select the disc image, and click Burn. With WinSetupFromUSB however, it's significantly more complicated. You will need to open the contents of the ISO file and copy them to your computer. There are a number of ways to do this, but I reccomend using 7-Zip and opening the ISO like a ZIP file. Now, open WinSetupFromUSB, and select "Windows 2K/XP/2K3 setup", and select the files you have copied from the ISO. Then, do whatever the program tells you to do, and presto!
Now that you have your medium ready, it's time to install! But not just yet. First, you will have to change some of your computer settings prior to install. When you boot up the target system, you will need to enter the BIOS. Search online what key you need to press to access it. In the BIOS (or BIOS setup), you need to find the SATA options (if any), and the UEFI options (if any). If there aren't any of either, then don't worry. It means your system is old enough to where it won't experience any real compatibility issues. In the SATA settings, make sure it is set to IDE mode / Legacy Mode / Compatibility mode. This is because Windows XP does not have SATA support out of the box. With the UEFI settings, make sure it is set to CSM, and that Secure Boot is disabled. Finally, save and exit the BIOS.
It's finally time to install XP! First, find the Temporary boot key. If you can't find it, go back into the BIOS and change the boot order so your USB / CD has priority. Now, if all goes to plan, you should boot into the installer.
Have a nice day!