Norton Antivirus 2008 with Antispyware

Pros: It has a solid feature set. Integrates well with Windows

Cons: Dear god does it drag a system's performance down

Summary: Put simply this is probably the most bloated, resource hogging, piece of crap software on the market today. Unless you have a computer with above 512MB of RAM and at least an Intel processor that is 2.5Ghz or better don't go anywhere near this software. (I can't stress RAM enough.)
It really is a pity too since I personally run Norton Corp Edition which I consider a fantastic product.