Geez, "format your harddrive" is the only advice anybody can give? You don't have to do that! This worked for me when I had the SAME problem:
"Explorer caused Invalid Page Fault in Explorer.exe": error at startup
It happened to me when upgrading from IE4 to IE5. The problem is caused when the system version of Explorer (not just the .exe) doesn't match what's found in the registry. The result is, Windows won't boot--even in Safe Mode--because Explorer crashes as soon as it starts. (from www.windowstrouble.com)
1) Using the MS-DOS Editor (because Windows won't load... :), edit SYSTEM.INI and change "shell=Explorer.exe" to "shell=Winfile.exe";
2) Start Windows, and you'll see the old familiar Win3.1 File Manager!
3) Hopefully, you have the IE5 install files on a CD somewhere. In that case, all you need to do is find the setup progam and run it. For example, in my case, I used the MS Office Small Business Disc 1. I clicked on the E:\ icon (my CD-ROM), then went to the "ie5\en" folder, and then double-clicked "ie5setup.exe". If you don't have Office, you can probably find IE5 on that AOL/Prodigy/MSN/CompuServe/Earthlink/etc. CD that you got in the mail last week, or in numerous other places (such as the place where you first attempted to install IE5, unless of course that was through Windows Update, which is inaccessible without Explorer)...
4) When ie5setup completes, the system will restart. You can then edit system.ini and change the shell back to Explorer.
Works like a charm! I hope you didn't listen the that great "format harddrive" advice!
