BillyS - 3:00 pm on Apr 15, 2010 (gmt 0)
XP required two reboots for some reason. I didn't pay attention, but I had a large number the first time, then two more were loaded and required a second boot.
I'm surprised the Windows 7 machine required a reboot. My Vista machine loaded the patches (I looked) and didn't ask for a reboot.