Erro: rundll32.exe is not a valid Win32 application

Microsoft Windows XP

Got stumped again by some XP problem. Usually I scour the net and withing a
few hits I can find the solution to my problem, but this one has been keeping
me awake for the last 2 days.

I cannot run anything inside the control panel (Add/Remove Programs,
Internet Connection, Date/Time. etc). Every time I launch an icon, this
rundll32.exe is not a valid Win32 app error message pops up. I've copied my
rundll32.exe from my notebook to my System32 folder, but it still does the
error message. Strangely, I can launch the shortcut for the Add/Remove
Programs, Set Date/Time via the the control panel (cpl) file. It's time
consuming to do it that way, but the cpl files are not corrupted.

I'm thinking that there is a line missing in my registry (don't ask me
where). I have one back-up of my registry going back 2 months, but I hate to
have to restore the thing and then re-install all of my programs. Likewise,
doing a comparison between the two is impossible as well. It's over 134GB in
size. Not to mention the numerous [CSLID-...] strings.

Does anyone have any idea how to quick fix this problem?

Thanks,

NVBB
Well I sure hope that it was a major typo that your registry files are 134GB
in size.

As for your problem I have encountered it several time before and have
always found that a repair installation is the easiest way to go.

The repair will replace the core operating system files but will leave your
files and settings intact.

http://support.microsoft.com/kb/315341