This morning, I made the mistake of installing Windows Media Player 11. The installer did it’s evil, and then lied to me, coaxing me to restart my machine to complete the installation process.

Well, restart I did, and up came the login prompt. Odd, I’ve set my desktop to automatically log in. But no matter… So I enter my username and password, hit enter and walk away. I come back, and I’m at the login prompt again. I swear I hit enter… So I log in again, and this time I notice that XP immediately logs me back out.

Uh oh.

Google wasn’t helpful at first. Everyone was blaming the spyware “Search Assistant”, but I knew that I didn’t install it, and that Firefox wouldn’t allow it to get silently installed. But, the problem was similar, and so was the solution.

I ended up adding two missing registry values to the key, by running regedit.exe on another machine on the network, and connecting to the problem machine by choosing “File > Connect Network Registry”. Here’s the key in question:

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWinlogon

The string values were:

Shell = explorer.exe
Userinit = C:WINDOWSsystem32userinit.exe

Hope that this information saves someone else a few hours!