Hi Bob,

First step would be to backup any important data.

Next run a thorough scan of the hard drive. To do so Boot the
system with a Windows Startup Disk. At the A:\ prompt type
scandisk C:  then press enter. Let Scandisk perform the standard
scan and a surface scan. When the surface scan is  finished remove
the Startup disk and reboot the system.

If that comes up clean do a search for any installed SpyWare/malware/adware:
Ad-aware is a free multi spyware removal utility that scans
your memory, registry and hard drives for known spyware
components and lets you remove them safely. After installing
Ad-Aware make sure to run the update feature before scanning.
http://www.lavasoftusa.com/  For large amounts of installed
spyware and such, it may be necessary to run Ad-Aware several
times to clear them all.

More tools that will do the same.
CWShredder:
http://www.spywareinfo.com/~merijn/cwschronicles.html
Download Link:
http://www.spywareinfo.com/~merijn/files/CWShredder.exe
Spybot:
http://www.safer-networking.org/

SpywareBlaster:
http://www.wilderssecurity.net/spywareblaster.html
SpywareBlaster doesn't scan and clean for spyware - it
prevents it from ever being installed. SpywareBlaster is
a non memory resident utility. It works by setting a "kill bit"
for the CLSIDs of spyware ActiveX controls, it prevents the
installation of any of them from a webpage.

For more information:
The Parasite Fight:
http://aumha.org/a/parasite.htm

Darnit:
http://www.mvps.org/inetexplorer/Darnit.htm#tshoot

Dealing with Unwanted Spyware and Parasites:
http://mvps.org/winhelp2002/unwanted.htm

If all this fails perform a clean boot.
How to Perform Clean-Boot Troubleshooting for Windows 98:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q192926

Please report back with your findings.