Howdy gang, My gf has a system that could use a CPU upgrade, but I'm wondering if anyone knows of a pretty solid way to avoid a total OS reinstall, if possible. System now has: Intel P4 2.4ghz, 533mhz Northwood (no HT) Asus P4P800 SE 2x1024mb Corsair PC3200/DDR400's in dual-channel As it's only running a 533mhz FSB cpu, the memory is only running at ddr-333 speeds, 4:5 FSB to mem ratio. It can gain a lot of performance going to 800mhz/HT P4 as it's a solid Intel 865PE chipset mainboard.. and I've got a P4P800E-Deluxe that yields the desired performance with a 3.06/800 Northwood core. In the past, when going from a 533-800mhz (and Northwood to Prescott w/ HT) update, even in the same motherboard, XP can sometimes get into the infinite reboot mode.. where the Windows load screen (with the green progress bar) will just yield a reset, then repeat ad-nauseum. I think it may be the HT causing this, even though her system currently reports the Uniprocessor PC in the Device Manager and is Pro vs. Home.. Local dealers are blowing out 800mhz P4/Socket 478's so it's tempting.. just really dont want to re-install this messy PC. Is there a way to do this without a total OS re-install? I'd prefer a simple CPU upgrade be a 1-2 hour thing rather than a whole weekend... she's got a LOT of crap on this PC I dread having to re-install, re-patch and backup/restore (her hard drive looks like her shoe closet...). All this work simply because her 6-story Sims2 house has gotten to the point of being unusable... sigh. Works great on my 3.0ghz system though, so we're hopeful this will last her until she decides to add a 7th story... lol. Thanks guys.. appreciate any insights.