Have Pentium II Windows 98 system. Mouse was not working, so purchased new PS/2. When installing, moved CPU to top of desk and unplugged everything attached then plugged back in. Now it loads Windows 98 and at screen where icons usually appear, it stops with message that says "no mouse detected." The keyboard, also, is not working. I tried another keyboard, but it too does not work. Is it a motherboard problem? Or are the two ports the problem? I am basically computer illiterate, so your help is appreciated.

what make of mouse and mobo are they?
And are the mouse and keyboard in their proper ports?

I had a similar problem where my asus A7V mobo wouldn't detect a microsoft intellimouse, which was annoying but thankfully it accepted a Logitech one I had lying around the house doing nothing.

The old mouse was original with the system (Pionex), but the new one is a Belkin. The keyboard is the original with the system also. At one point I got a message at boot that said "a DOS file APTI18 is missing in config.sys file"..but it loads to Windows 98 and I can't use keyboard or mouse to load in safe mode since neither is working. I appreciate your help.