Error Occurred (0) at startup

I am running a Dell Dimension 9200 with Vista Home Edition. A few days ago
we had a power failure. When I rebooted the computer it came up with a
message at the early stages of rebooting saying 'Error Occurred (0)' in red
for one of the disk drives. The other one is fine.

It goes on to load windows, and I can get into Vista and run most programs,
but it does not run IE7, I cannot get any internet connectivity, it will not
run OneCare, and it cannot find any of the netwrok drives that are connected.
It also comes up with a message 'ATI External Event Utility has stopped
woking and was closed'.

I have run the windows doagnistics tool that goes through all the disk
checking at start up and it did not come up with any errors. I also ran the
Dell diagnostics (I think f12) and it did not find anything. I have run disk
cleanup and am busy runnign defrag.

Any suggestions on how to fix this problem?