Even though Vista SP1 faced numerous delays and was just released this week to the general public on a planned staged roll out, it seems Microsoft still has to hammer out all the bugs involved with the pack. A number of users are claiming the update damaged their computers. One user complained of the update disabling video card drivers, others complain of it causing blue6 screens, or even additional memory usage after installation.
Service packs have always been a touchy subject with Microsoft. If you may remember, Windows XP SP1 was no picnic, and SP2 was a veritable nightmare for many. Yet, in the end, it always ends up being the best idea to update machines. Microsoft has put some checks in place to make sure it isn't installed on systems that have incompatible hardware or drivers, but with such a plethora of hardware out there it's simply impossible to catch them all.