Start with the Win98 floppy disc you can create one if they have the Win98 disc by going to add remove in control panel. then start the comp with the disc, and type scanreg/restore hit enter it should look like this in DOS
A:\>scanreg/restore then choose the oldest date. If thet does not do it.
Go to start/run type SFC and run with the win98 disc in, you can go to the settings button and click look for deleted files also