Trouble installing bew 7600GS video card

I'm having trouble installing my new video card, an nvidia 7600 GS AGP card with 512MB RAM. I'm replacing an ATI Radeon 9800 All-In-Wonder card, also an AGP 8X card. Old card has occasional fan trouble, so need to replace it.

I uninstalled the old drivers, shut down the computer, and installed the new card. I handled it carefully, made sure it was seated correctly, hooked up power to it, hooked up the monitor (same one that worked with the old card), and started it up.

I get a blank screen, then test appeared in the upper left corner listing the specs of the new video card, then nothing. Hung up there forever. Restarted the computer, then the screen was blank and the monitor told me it was not receiving any signal.

For giggles, I re-installed my old card again, computer booted up fine (albeit with no drivers for the old card now). So, tried the whole thing again with the new card, same result.

Help!

Here's my system (also listed in my profile):

Asrock K7S41GX motherboard
AMD Athlon 2800 CPU
1.5 GB RAM
160GB harddrive
DVD-ROM
CDRW
floppy is disconnected right now.
300W power supply (which the card specs say is the minimum for this card)

Thanks.