Are you running Windows 98 SECOND EDITION? If so, please install the Windows 98 Second Edition shutdown supplement from the link below:

Windows 98 Second Edition Shutdown Supplement

The EXACT error message would sure help.

Please follow the instructions in the links below. It may take a little while, but it should clean out some of the stuff causing your issues.

First, because you didn't mention it, please download, install, update, then run the free spywarer removal tools from the links below. Delete all spyware that they find..:

Ad-Aware">http://www.lavasoftusa.com/support/download/]Ad-Aware