I can still run programs from the control-alt-delete task manager, under file->new task (run)
sfc /scannow has no effect without the repair CD
Restoring to previous points in the registry has no effect. (I'm reasonably certain these points were before this issue began to occur, so that should have fixed it if it was a registry issue.)
It will not see my USB drive, so copying over explorer.exe from a working computer wasn't possible.
I downloaded "fixdesktop.zip" from somewhere, and although it claims to not be able to locate the file at c:new folder/fixdesktop.zip, it will jumpstart the system temporarily and give me the desktop icons, taskbar and start menu for about 20 seconds, and then they go away again. After a few seconds, they sometimes reappear, only to disappear again after several seconds. That process may repeat a few times, and then it stays gone until I try to run the fixdesktop.zip again.
I've watched the processes list when I do this, and Imapi.exe comes up after and disappears before explorer.exe, but from the research it appears that this is a harmless program and it does that anyway.
I've downloaded a couple of other tools (one from a Kelly's place that I can't recall) and it didn't help. A couple of the others (dial-a-fix, for example) come only as zip archives, which the computer claims it can't locate, even though I browse to it on the C drive to open it. I just now figured out that I could browse to it in internet explorer and extract, and that's my next step if I can find the page that told me how to use it.
One curious thing - It needs a defrag and I need to delete the old user information anyway, so I deleted the additional users that I didn't need. I then set up a new account for myself and logged into it, but I'm not able to "kickstart" the taskbar and icons into appearing here by trying to run the fixdesktop. When I try, it pops up a window briefly that it's setting up user preferences for internet explorer, then that goes away. It feels like that should be a big clue.
I'm very close to stumped. Anyone have any ideas on how to proceed?
Thanks in advance for the help.