Beware that some mobos made around 2005-2006 were known to have a bad batch of capacitors and the increased heat load from the card may be enough to do them in. I'd inspect all caps for bulging/splitting before starting up the rig.
Thank you. I've been gaming a lot with my current card (gf 8800 gts) and it's temperature can occasionally jump as high as 90-100 °C. Besides the occasional freezing (only in a few games, weird) I had no problems in the past 4 years.