You can, but then you can't. Since the card is in PCI format, rather than AGP, your overclocking abilities will be severly limited. If you still want to OC the card, then I'd suggest to look for a registry key on the internet called 'coolbits.' It has proven itself over time and I even use it. If you are uncomfortable with having a registry key changed, then go to
Omega Drivers and D/L their nVidia drivers for watever OS you're using. I hae also used this, and have pushed my FX5600 XT
way further than any average user would like to go. But, that was after I put on an aftermarket cooler. Also, the card was in the AGP slot. It's up to you which one you want to use, I just provided the information.