Maintaining PCs at work

I work in a small office and I have been chosen as PC troubleshooter coz those grey boxes under the desks don’t scare me!!. We have four PCs and two laptops and some staff members try to tweek the PCs with often disasterous results. Is there any way I can technically stop staff members from accessing the control panel, add/remove programmes, so that I can keep an eye on what goes on and comes off the PCS. We are not networked. We use Win98.
Any help will be rewarded
(with points!!)
Katey