need help with new mobo

adding new Mobo &CPU to old system and didnt know if i should clean my hard drive and then reinstall xp,or can I boot from what information i already have on my c drive?

Being that you're running XP, it will automatically recognize the fact that you've installed the new mainboard and regardless of if it boots ok, will prompt you to re-register with MS. I've had this happen a couple of times, once when I installed a new graphics card and again when I upgraded my DVDRW drive.

If you're using an OEM version of XP, you're screwed. You're only allowed to have it installed on one machine, i.e. one mainboard. If you've got the regular version you're ok.

Otherwise, it should start loading drivers for the new hardware it finds. Just for argument's sake, you'll want to backup any critical data before you do anything.