I have an Intel Pentium III and after teh SP3 Windows update my computer went into emdless reboots. Microsoft never told me that other customers had similar problems. It is 4 days now - my system was rendered useless - repair options caused even more problems because they had me repair Windows from my original Windows CD (SP1) while the IE7 was still in my system. You figure that someone woulf have thought to send me the CD with the SP2 pack on it so the repair would not conflict with IE7! They are so cheap - it is unreal. The fact that they proceeded with the repair using the original CD (without SP2) while the IE7 was not first removed corrupted Outlook and Outlook Express and messed up a whole bunch of dlls which failed to load during repair.Now they are telling me that I have to reinstall Windows XP!
Please do not let them give you the big run around that there is something wrong with your system. It is the stupid SP3 that sends your pc into endless reboots. And, they are not even admitting it!