I'd recommend starting from scratch. You might still need to rummage around the internet for drivers for your accessories, but at least Windows itself won't be corrupted.
Follow the instructions here - print them out!
http://www.d-a-l.com/reinstall-win98.php
I particularly draw your attention to the fact that you must create a (floppy) boot disc first, in order to be able to do the reinstall. This is because your PC may not be able to read its CDROM drive without the CDROM driver that the boot disc contains.
I've successfully used the boot disc available at:
http://www.bootdisk.com/bootdisk.htm
It's advisable to RESTART the PC after installing each driver (whether prompted to or not).
The first website you must visit as soon as you have your internet running is:
http://windowsupdate.update.microsoft.com
All the Critical Updates that Microsoft released are still available there, it's just there aren't any new ones after Summer 2006!
Regards
SS
November 2007