Win XP SP2 - Some .cpl's not working and welcome screen gone

Hi - I've been looking for three days for an answer to these two (related?) problems on my Win XP SP2 installation.

Add/Remove software has disappeared from my Control Panel. Before that, it just didn't work (I clicked & nothing happened). Also, most of the .cpl's in Administrative Tools don't work (eg Event Viewer). I have tried to execute the .cpl's through the command interface, but to no avail... Re-linking the .dll gives me an error (Loadlibrary failed - A DLL initialization routine failed).

Secondly, I no longer seem to be able to re-enable the welcome login screen (got the classic one now). I have tried to re-enable it through the register, and by trying the settings in User Accounts. No luck, though.

I seem to think it has to do with the a recently installed hotfix, but I don't know which one, as Add/Remove doesn't work anymore!

I have this nagging idea XP suddenly thinks it's on a domain - hence the lack of a welcome screen, and hence the way I'm no longer able to add/remove software and use the Admin's control panel (I am an Administrator of this machine though). It's as if XP's confused

Oh, and another thing: all versions of TweakUI I tried "failed to initialize".

Anyone? I'm getting pretty desperate about this.

 

I would do a repair reinstall of WinXP.