This also happens on windows 7 rc. when u have an improper shutdown (power outage, forced shutdown by holding power button down or reset) it can happen, that windows starts to get stuck on the welcome screen.
Solutions:
When you choose to boot in safe mode, the next restart will work fine until you have an improper shutdown again.
Repair will work as well. but takes much longer then the above solution.
I have not had that issue in the beginning as far as i can remember. But somehow down the road it happend although i did not install any additional software. All my windows 7 platforms are running windows security essentials beta (Morro), Adobe CS4 Master Collection, Magic Disc and Magic Iso, WinRar, Office 2008 Ultimate, Visual Studio 2008, Expression Suite and Skype. It might be in connection with the CS4 update because this is the last changes i did before this happend to occur. But i doubt that and think is rather more a kind of a bug and will solve itself by time. after all this is the ONLY problem i had ever with windows 7, beats vista for sure (which is crap in my view) and even is faster than XP in any competition you put them side to side with the same configuration. And on top of that, it can even handle older programs just fine even xp itself had drouble working on correctly. P.E. with win7 you can play every GTA game (from the first to the last one released) on steam, which doesn't work on xp or vista fully. when you read that something is not supportted don't take it for granted and try it in the compatibility mode. i got software to work lilke macdrive which is not supposed to though, just by changing compatibility and admin rights.