computer freezing ???????

[Taz202]

I recently upgraded my computer with a 256mb pci video card, BFG 5500 oc, (no agp slot) as well as a 300w psu. brand escapes me at the moment, though nothing I recognized. I was having problems with the computer running slow, therefore the upgrade. I had onboard video before that. Now the computer runs faster but is more unstable as it frequently stops responding and requires a reboot. I have an older mobo and was told that maybe it needed to have the bios updated. I tried this and ended up being directed to a informed me that it did indeed need updating but it would cost me about $60us. I can probably buy a new mobo for a little more so I cancelled that idea. I finally found a site with updates I could download but there were tons of them and I could not make head nor tails of which ones I needed. I did manage to find one download that was supposed to be an update but it did not cure my woes. I'm wondering if reformatting my hard drive would help me out. I've only used about half of my 12.7gb hdd. so I don't know if that would be a factor or not. Any thoughts on this would be greatly appreciated.

Thanks

Here are my specs if it helps
VIA VT8601T Appollo PLE 133T
Biostar M6VLQ
celeron 1.3 Ghz.
192mb SDRAM
NVIDIA Geforce FX 5500 OC
Win 98SE