SLUI.exe fails to initialize properly in Vista Home Premium

I originally posted this in a thread under Dimension hardware as it began as a problem discussed there. But no reply so far, and it looks like a software problem anyway. So here goes again....

 

Writing here from Hong Kong, but not able to find anything on the local Dell site, and the local support people have only suggested reinstalling Windows, which is less than helpful as I've already stored a mass of stuff on the hard disk. So hoped I might find some help here.

 

I had a problem with "Missing operating system" on a new Dimension 9200 (sold as E520 in the US, I think) running Vista Home Premium. After a couple of weeks running with no trouble, I shut the machine down and tried to boot up a few hours later and got the "Missing operating system" message. After running all the hardware diagnotics from the F12 boot options menu, which all passed, I eventually found the Repair System feature on the Dell reinstallation disk and this fixed the problem and I can now boot into Windows OK. But now there's another problem. I can't log into any of the user accounts. I just get this message:

"SLUI.exe - Application Failure

Application failed to initialize properly (0xc0150002). Click OK to terminate the program."

 

I know this is something to do with the notification and activation service and if I don't clear the error message, once the computer has connected to the internet a message comes up to say my copy of Windows is not genuine. I can boot into Safe Mode, so long as its not Safe Mode with Networking (that tells me I need to activate my copy of Windows). Seems like whatever file or piece of information that identifies my Windows as a genuine activated copy is now missing, corrupted or in the wrong place.

 

Can't find anything on the forum for this. Can anyone help? I really don't want to re-install everything.

 

Cheers!