People have asked which Linux is best for XP users to upgrade to. Your hardware is still fine but Microsoft is ending support for XP - Linux will let you keep your hardware running without spending a penny. Granted, you don't have to spend a penny to keep XP, but you won't get any more security updates (and you know what that means for Windows).
And so here's Linux Mint, a very easy transition from XP. The introduction:
The installation (go to Youtube if you want the video on setting up dual boot; my opinion is that dual boot is for Communists and farm animals, and you don't want to keep XP around - no security updates, right?). Remember, you will have downloaded the Linux Mint 32 bit ISO to, say, a USB drive and double clicked the ISO:
What to do after installing:
Remember, it's minty fresh! And Linux is magic!