Winword.exe

I can not open Word documents and get a message that winword.exe is missing. I tried to reinstall Office 97 (Windows 98) and got a message that it could not reinstall because D:\OFF97INV.DLL was missing. When I hit ignore, it said D:\ACME.exe was missing, etc, etc, etc. through many files.

I thought perhaps I had a virus, but I updated my virus definitions and found nothing. ScanDisk shows no problems either. HELP!