Service Pack 2 includes a lot of security updates
It's important to install it
However, there are some incompatibilities with Drivers that are out of date
and some third party software programs>>Such as ZoneAlarm
If not updated
ensure to keep Drivers and programs up to date
Also, recommended by Microsoft
Make sure your computer is virus and spyware free before you install Service Pack 2
This is necessary
At one time one of of ten computers were having a hard time after installing SP2
The blame was put on the service pack
Digging deeper they concluded that Most, I'm not saying all
Had either Virus, Trojans, Spyware,etc.. on their computers before the install
Or older incompatible software