Explorer invalid page fault hangs Explorer

Windows 98 Explorer keeps hanging up unexpectedly, usually after I close a file I opened by clicking in an Explorer window, sometimes after I delete a file, or transfer files to a different folder. If I have more than one Exp window open, it sometimes will close the others as well, and sometimes even the Internet Explorer or Opera windows that are open. An eg of an error message is something like:

EXPLORER caused an invalid page fault in
module <unknown> at 0000:01bb32f4.
Registers:
EAX=00000000 CS=0177 EIP=01bb32f4 EFLGS=00010202
EBX=008dfa58 SS=017f ESP=008dfa08 EBP=008dfa24
ECX=01d60ff4 DS=017f ESI=00008a7c FS=10e7
EDX=00008a98 ES=017f EDI=008dfa0c GS=2e17
Bytes at CS:EIP:

Stack dump:
bff7363b 00000f74 0000001c 00000000 fffe0c6b 8a562e4f 0000017f 008dfa38 bff942e7 2e178a7c 00002e17 00000000 bff719b8 008d8a76 008dff88 bff7186d

I think the problem started when I ran a registry diagnosis and fix program which started "fixing" without warning. I have tried various fixes, including reinstalling 98 OS from the CD (without reformatting the hard disk), but nothing works. Microsoft Support advice for this kind of problem doesn't help either.

I copied the root directory and the Windows folder and subfolders to CD-s some time before the problem starting occurring. I recently backed up all of my 4 gig hard drive to a 250 gig USB hard drive - done after the Explorer problem started occurring. I don't have disks for expensive programs such as Word, Excel and Mathematica. Reinstalling 98 without reformatting doesn't affect these programs, but doing it with reformatting, will lose them. Is there any way to recover them from the back-ups I have made?