I had SP-2 install problems on 2 computers however after reading the install tips on the MS update pages, all went well.
First, make sure you have scaned your drives with updated anti-virus,anti-spyware programs. Second, clean and defrag your drives. Next, install all updates, reboot, check your operating system. Now, your ready for SP-2. I have noticed a slow down on bootup but that is due to the new firewall, anti-virus checks provided by SP-2. Good Luck.....