MAC do have more exploits than people are aware, just because Apple suggest there is no viruses, doesn't mean there is no exploits. MacOSX is built on BSD, which is Unix and there is that many exploits for Unix it's not funny. It also depends on services that are also running on your Mac.

As for the actual PC issue, maybe some screenshots of the information thats in your startup tab in msconfig (ie goto start>run>msconfig)

Also it's probably best to have a task list, so goto start>run>cmd and type in
cd C:\Windows
tasklist > a.txt
a.txt

It should open in notepad, just paste the contents