I recently installed Windows 7 on my HP pavilion. When I start it up, I get the initial diagnostic screen, then it goes to a black screen (with a blinking white underscore in the corner) for at least three minutes, before loading the Welcome screen normally. I've tried running a startup repair from a Win7 repair disk, but it reports no problems. I've also tried running a registry check, reinstalling drivers, and resetting the "timeout" time. Nothing affects it.
On top of all that, I can't install any updates without getting various critical boot errors. Windows recovers from those after a single restart, but that means I have to suffer the 3 min. black screen twice in a row.