Symptoms:
After startingup WindowsXP the computer isn't reacting when I click on anything on the desktop or the taskbar. Hourglass over Taskbar.
When I end the explorer.exe process(0% CPU) - it sometimes restarts automatically and sometimes I have to restart it in the task manager(new task->explorer) - everything works, but explorer.exe randomly crashes when I use the Windows Explorer, i.e. it may crash when I open a folder, open a just created new folder, scrolling in the Explorer, or when I just minimise the Windows Explorer.

Tried:
Virusscan(Bitdefender Free Edition)
system restore(but I think the restore point is not old enough, anyway, didn't help)
sfc /scannow
chdisk

Notes:
Don't think it has anything to do with thumbnails. Don't want to reinstall windows.

Hope someone has an idea

A repair install maybe your best course of action especially if you don't want to try a full rebuild.
Here's (http://www.microsoft.com/windowsxp/using/helpandsupport/learnmore/tips/doug92.mspx) the official Micro$oft way of doing a repair install,
And Here's (http://www.geekstogo.com/forum/index.php?showtopic=138) one with screen shots.

The good thing about this method is that it keeps all of your current settings.

The trouble is I have only Recovery CDs, no repair installation possible with them:( .

Actually I have most of my programs on a different partition, but the sad point is some parts of the programs are put on the WindowsXP drive, anyway(e.g. dlls). Guess there doesn't exist a tool copying all non-windows files+registry+... and can put them back after the reinstall(or does it?), so reinstalling is not really a sensible option and I am not aware of any way using the recovery CDs somehow to repair/replace the explorer or to repair WindowsXP as a whole.
Maybe you know a way? Or do you have another idea?