First off, CoreCell is more of a backup BIOS than an overclocking tool, but that's not a big deal.

You basically need to be kind of careful when overclocking by just bumping up the FSB speed, but you've already found out why.

There's two ways you can fix this, which amount to the same thing. First, check the manual for your motherboard, and see if it has a CMOS reset jumper. If it does, use that to reset your BIOS to defaults. Otherwise, pop out what looks like a large watch battery. Give it a couple of minutes to be sure, then put it back in and reboot the system. You'll have to redo some of the CMOS settings over again, and this time you might want to be a little more careful with your overclocking. You want to start small, like a 5MHz increase, and then see if that's stable for a few days... Then bump it another 5MHz, lather, rinse, repeat until Windows starts crashing or freezing, then slowly back it off until it's running stable again.