The registry is the guts of Windows95.  It tends to replace a lot of text
based initialization files (ini files) for most 32-bit applications.

If your system cannot find it's registryt, you have a big problem.  Here's a
possible fix.  Start the computer in "command prompt mode"  Do this by
hitting F8 during boot time, and selecting the proper selection from the
menu.

Change to the C;\windows directory.  run the commands "attrib -r -s -h
*.dat" and "attrib -r -s -h *.da0" .  Delete the files user.dat and
system.dat.  Rename the files user.da0 and system.da0 to user.dat and
system.dat.  This restores the registry from (hopefully) clean backups.

Reboot.  All should be better, but to be safe get a copy of RegClean from
the MS web site and run it a few times to clean up any messes previous
installs may have made.

As Gerry mentioned, the Registry is a giant database file that stores all the settings for Windows and your other software.  If you have done all you mentioned, the backup .da0 files are overwritten by now, as they are replaced on each boot.

You may have a memory problem (RAM), as also indicated by the "xms cache problem".  When you started in Safe Mode, and it said on-screen "testing extended memory....", did any messages appear at the end of that line, or did it just say "....done"?

I would have the RAM tested. There is a software tester that you can download and try first....it creates a boot disk with the RAM testing app on it, to run from a boot from the floppy:
DocMemory
http://www.simmtester.com/page/products/doc/download.asp