1) What cooling have you got? If it's a poor Heatsink or not seated squarely, that can cause problems.
2) Do you use Thermal Goop? If so what type? Thermal Goop (Paste/compound) is vital in these days of hot-running CPUs. It aids heat transfer to the CPU.
3) What RAM you got? PC66 Might not like running at 100 (even @ CAS3).
4) What PSU you got? OC'd CPUs use more power than std. A 300W Athlon Capable (if not approved) is what I'd recommend if your OCing anything (it'll power all the cooling fans you might wanna slap in, too)
The BH6 is a good starter's board (I used to have one before it died). It has voltage adjustment in the BIOS, as well as 66, 75, 83,100, 103 (Turbo),112, 124, 133 MHz FSBs
What FSB are you trying to get it to? Don't try to get it to 100 at first. Try 75 and 83 before going for 100+.
Your Heatsink might not be seated properly...
The BX northbridge can get a bit too warm, if it's been removed and not replaced properly.
You can use SoftFSB to adjust the system bus under Windows, so if it freezes, all you have do is reboot the system (no digging for BIOS reset Jumper).