One for the computer guru's among us...;

I have been given an older PC, which is running Windows 8 as it's OS, but it is very slow and prone to crash. Upon investigation, I have found that Windows 8 requires a minimum of 2gb RAM to operate, however this machine only has the capability to take a maximum of 2gb. I suspect this is the primary cause of it's problems.

What I am wondering, is can I install XP over Windows 8 (ie a clean install of XP) as XP is far less hungry for resources and should be more stable. If so, how is it done? I have an XP Home CD and original product key from my old deceased laptop, and this machine runs DDR400 RAM so I cannot go any larger with that either.

Thanks for any input you may have.