I've had an issue with some older hardware I have. When starting Windows, during the "progress bar" screen during boot-up, as the screen fade's in, the computer freezes. After about a 2-3 minute pause, the screen fully fades in, the progress bar does it's animation, and Windows boots fine. This made it very inconvenient to turn the computer on at times.
Originally I thought it may have been a bad file during Windows boot-up, but the problem existed between installations of Windows XP, Windows Vista, and Windows 7 RC, every single instance pausing at the same part of boot-up, during the fade-in of the loading screen. The problem wouldn't happen immediately though, and usually it would be about a week after reinstalling the OS before it would freeze like this.
I did have another issue with the RAM, where the sticks would not request the proper voltage and would clock to a slower speed, at which point I used the motherboard settings to set the proper voltage and speed. Changing this voltage would sometimes fix the issue temporarily, although I could never determine an exact pattern on when this would happen and wouldn't.
So does this indicate bad RAM? A faulty motherboard perhaps? There is no stability issues once Windows starts up, just getting into Windows takes forever. Running memory tests have never returned issues.