The keyboard had to be a Dell or you could not use the keyboard. However given how old XP is, can you tell if you cleaned the vents and heat sinks?
Light reading of similar story at link.
A couple days ago I unplugged my usb keyboard on my dell dimension e310. When I went to plug it back in a few days later it would not work and the mouse stopped working. After trying several different things I read online I decided to do a repair install of XP. The mouse and keyboard are both usb. I am able to use both at boot including keyboard at bios and mouse during the repair install until it gets to 34 minutes "Installing Devices". For what ever reason between 34 and 33 minutes the mouse and keyboard quit working and then the regional and language settings pop up. I am stuck on this screen because I cannot select anything. Please help. Even when I turn it off and back on it keeps bringing me back to setup.