I too am having this problem. I'm using a perfectly legal copy of Windows XP Media Center Edition on a brand new Alienware laptop. I recieved the laptop a couple of weeks ago and did a fresh install whenever I noticed that the Media Center wouldn't open correctly. I looked up the error on the internet and most everything I read pointed to a .NET problem. So I followed Microsoft's steps to uninstall and reinstall .NET. Didn't work. So I formatted the computer. Media Center opened fine for the first few times...until it updated to .NET Framework 1.1. So I formatted it again. Alienware's got it's own installation procedure and automatically installed .NET. So I waited until .NET 1.1 was updated. I hesitantly clicked on Media Center...and it worked. ?? And then, it didn't work. So I formatted it AGAIN. I turned off automatic updates from Microsoft and it worked like a champ. But then there were about 50 other security updates (thank you, oh Hole-y Microsoft...) that needed to be updated, among which was a .NET framework 1.1 security update. I installed ONLY that update. Guess what: Media center DIDN'T F**ING work! Big surprise! Formatted it again, COMPLETELY CLEAN FORMAT, NOT QUICK FORMAT. Did the same thing. Now I can't run anything because of this stupid error. I've checked for viruses. Nothing. I've installed .NET 2.0. Nothing. It won't let me install .NET Framework 3.0 either, so yet another dead end there. So basically, I've got a $3500 paperweight because either Microsoft can't get their s**t together or there truly IS a problem out there that people just aren't finding (ie-virus software companies) which is just scary. If anybody knows what to do to fix this, I'd much appreciate it. I can only run a handful of programs which is severely hampering my work.