The original GF 256's suck a LOT of power from the AGP slot and get VERY hot. Think I've seen temps of 80C+ reported, when measuring the back side of the Vidcard, opposite the GPU. If you're concerned about the heat there are a number of options. The easiest is to buy a Card Cooler. These blast your Vidcard while hanging above them, and are affixed to the screws that hold PCI cards in place. The latest model of the Card Cooler is the XT, AFAIK. It features two 120mm fans and moves a LOT of air. Simply pushing hot air around a case with poor air volume throughput is kinda less than smart, but the XT model is said to be worthwhile.
If you're not concerned about voiding your GF 256's warranty, the ~40mm fan that's on the card's HS can be replaced with a honkin' 40mm. While "honkin'" and "40mm" is usually oxymoronic, there is a 8 cfm 40mm--this is nearly 3 times as powerful as the little very thin 40mm's.
It's more effective to remove both the fan as well as the heat sink from the GPU, and replace them with a sure 'nuff big HS, and a 50-60mm real deal fan. Depending on your card's manufacturer, removing the OEM HS can be a VERY dangerous procedure. The top of the GPU itself can accompany the HS.
A HSF can be installed opposite the GPU, on the back side of the Vidcard. This is also somewhat of a ticklish operation.
The best way to cool down the GF 256(and the rest of your components) is with good case throughput. 50+ cfm will help.
The truth is that 54C is a normal GF 256 GPU temp, and is not worth worrying about. This may change in the summer.