I've noticed a lot of the newer (post-6-series nVidia) cards run rather hot. I kept freaking when my 8600GTS kept hitting 60, but my new 8800GTS 512 regularly runs at 70, with stock clock. I remember my last card, a 6800GT/GS, only topped out at 50 in summer after fooling around all day.
If that's the EXACT card you're using, then it's passively cooled (no fan), and relies on those metal fins to cool itself. If it turns out that the card IS running hot, I would suspect airflow in the case is bad. A little cable management and maybe some new fans would do the trick. If that didn't work, I would consider a case swap, but considering the age of the machine in question (no offense), it may be time to begin the process of learning to build your next one.
Of course, if you're not playing very many games or doing anything really performance-critical, you could also download Rivatuner and downclock the card a little to resolve the heat issue if it really bothered you, such as if it caused graphical artifacts or crashed the system now and then.
But frankly, unless it's hanging the system, shutting itself down, or downclocking itself, I would say that its temps are probably just fine...let it burn, baby!
