was wondering if installing the service pack is a good idea? does it improve performance much? also, does installing it require any type of "registering" online type of crap? (don't wanna mess up my friends cd-key)
If he is using an illegal cd-key then he will have to change it. If he isn't, then you can just install it. It doesn't do anything good or bad really, but it avoids having to download all the updates at the very least.
There's a whole slew of threads with this question. Search on your left for sp1 and go back a few months.