If it is running too hot (e.g. over 85c) then yes. Considering how weak a 9500GT is, there is a limit to how much performance you'll get out of it. If you're wanting to play [newer] games, a HD5670 or even a HD5570 will give you the improvement you need, for around $100 or $80.
If you can't increase your fan speed with the nVidia control panel you need to download a software that can do it like Rivatuner.
GPU temperature below 80C is OK. Setting the fan to a constant 100% speed will shorten its life. Try to find the right balance.