One of the reasons that I decided to do a clean installation of Windows is that sometimes it seems that activity on boot sometimes simply ceases for a prolonged period of time, like a minute or two with a black screen after login. So far I haven't experienced that on the new installation, but did just get a similar delay on the shutdown screen. Everything I come up with as a possible answer to the problem doesn't pan out, because I've run every hardware test I can think of and found no problems. The odd part is that during these delays, I can't hear any hard drive activity, like I should on a WDC 64 bit cache drive. When I do finally hear activity, the boot or shutdown may continue normally, but on the last boot to the old installation the drive had to rumble for some time before the black screen was replaced by the desktop. Since the old and new installation are on two separate drives, of which neither show any problems on testing, it seems unlikely that the drives are the root of the problem, and since the RAM tests okay, it would appear that the only thing left is the motherboard. Does this conclusion make any sense? Is there something else that I should consider?