I won't bore u with extreme details so here are the basics

Click here to proceed to download the stand alone patch
Its a massive 273 MB
It will work on pirated versions of Windows XP MS said.

Rumours I heard that 1 of 2 things. It will either completely boost your PC preformance or screw things up. But those are only rumours. Probably kinda true for those ppl that have screwed up their PCs anyway and complain to any patch upgrade.