I've seen a lot of folks who are working on monitors that "flicker," causing eyestrain and headaches, especially when the monitor is in a room that's illuminated by flourescent lights.
Often a quick and easy solution is to change the "refresh rate," which is a setting in the "Display" program that's part of the "Control Panel" in Windows. On my Windows 98, you'd click Start -> Settings -> Control Panels -> Display (double click) -> Settings (a tab) -> click Advanced button -> look for an Adapter tab -> look for a Refresh Rate setting.
Try setting the Refresh Rate to the highest value in that list -- 85 Hz or 75 Hz, for example. And try "Optimal" and "Adapter Default." Windows 98 lets you preview how the monitor will look under the new setting, so you can go back to the current setting easily if the new setting is no better or causes the monitor to act strangely.
Sometimes the difference is truly amazing. While visiting my accountant's office I made the change for their receptionist, who now thinks I walk on water