Here is a Microsoft article about that error and the fix should work.:
Err Msg: Notepad Caused an Invalid Page Fault in Module Notepad.exe...
If you think you need a new "Notepad.exe", you can replace the one you have by simply making a copy of "Notepad.exe" from another Win98 machine and replace the old one. Not all "Notepad.exe" files are the same, so it would be best to make a copy from a Win98 machine.
Hope this helps.
I use Window 98, for some reason my Notepad has been damaged. Is there a way of replacing, re installing or fixing it?
Every time I try to open an attachment in .txt format, I get an error message saying: "This program has performed an illegal operation and will be shut down. If the problem persists, contact the program vendor."
And if I click the detail, the message goes: "NOTEPAD caused an invalid page fault in module NOTEPAD.EXE at ..."
Any idea how to fix this?