It sounds like "DLL hell" strikes again. I guess, you'll have to reformat your HD and reinstall WIndows. I would recomend to move to WIndows 2000.

>Several months ago, my InstallShield 6.1 starting getting an IDE invalid page fault in mfc42.dll. I have tried all kinds of thing to get around this, renaming all copies of mfc42 to something else, reinstalling, etc.
>
>I am able to physically switch my C: drive to a differnt C: drive and reboot with that with a different Windows 98, and run InstallShield from the same set of files. So its not the hardware or install CD.
>
>The problem is that every time I need to build an install, I have to power down, switch the C: drive and reboot.