replacing motherboard and cpu everthing ok?

[limousineorama]

i just replaced my motherboard to a Asus P5K-E with a quad core intel cpu. im running vista home premium as an upgrade from xp. As i plugged it all in etc i expected to have problems booting up etc but it booted up as if nothing was changed, although it recognised all the new hardware and i install the new bios and everything is good. the only problem is that the hard drive is always being accessed as if its running some intense program. i checked the cpu usage and its only using a small amount but the computer speed is slowed down because of the hard drive being in use all the time. its is a SATA 500gb. Any ideas of why this is? should i just go ahead and wipe the drive and install everything from the start would this help or possibly fix the problem??

thanks