Make sure you dont have any programs running in the background (ie. you system tray)... a good way to find out what you have running is to do a check...
In case you dont know how...
Click start, run, and then type msconfig, click OK and click the startup tab.. and all the checked boxes are what your system loads up and may be running in the background without your knowledge. Just be careful on what you uncheck. If your on win98 dont uncheck Explorer and Systray otherwise your not going to reboot to windows.
A good place to go to, to test your machine for free and get an profile of your running programs in your msconfig settings is
PCPitStop. Once the test is done it will tell you if you have any spyware/viruses on your system and whether or not you need some background programs running or if they are just taking up memory doing nothing.
Hope this helps.