I used the power adapter that came with it. I have a good ps - 550 watt so I don't think its the problem - it fixed my low 12v amps with the 7800gs I'm trying to upgrade. I have a new 750watt ps I'm gonna try next.
TilDeath - you don't think the card is enough of an upgrade to see an improvement in AH?
Contrary to some comments, the ATI 3850 is actually a pretty good card, even the AGP version. You just need to make sure that you are using the
ATI 8.12 AGP Hot fix drivers. Also, that article that was quoted in the post above mine, it's incorrect. The ATI 3850 has full Vista support, it has to as it is a DirectX 10.1 compatible video card.
Your power supply should be fine and most likely is not the issue. I would guess that you need to make sure that you are doing a clean install of the drivers. In the Add/Remove section in your control panel, run the ATI Uninstaller program and follow the directions. Afterwards, reboot your computer. When it reboots, the Add New Hardware wizard will start, hit 'Cancel' to stop it from running. If you haven't already downloaded the hot fix drivers do so now (save it to your desktop). Double click on the hotfix driver .exe file and follow the instructions to install the drivers. Reboot your computer and then adjust the settings to your liking.
You've probably already done this but make sure that your AGP port speed is set to 8x speed. This can be done in your BIOS.
Hope this helps.
ack-ack