Hello, I currently have a XP Professional without any of the service packs.
There were two problems that prompted to install the service packs:
1) None of my USB devices worked, EXCEPT my mouse, which is connected through USB (SP were supposed to support them)
2) My 320 gb hard drive displayed as 127 gb (SP was also supposed to resolve this) My bios, however, correctly shows 320 gb.
Now, when I try to install SP1 or SP2 (I tried both), the aforementioned hard drive issue is not resolved. More importantly, however, my USB mouse stops working, nor does XP detect any other USB devices.
So everytime, I am forced to system restore.