Anything found in the Start->All Programs->Startup can be deleted (by right clicking it and selecting Delete) without worries. But this doesn't usually show malicious programs.
Without you having access to someone knowledgeable who can look at your computer in person, a reformat is not a bad idea. Just make sure you back up everything you want (saving your My Documents folder is usually a good idea). I had the exact same problem as you (with the exact same reaction
) so I know how you feel and in the end I had to reformat my hard drive to get it back up to speed. I'm just lucky my hubby is a talented IT engineer and has helped me learn how to keep my computer running smooth since then.
My best guess is that you've got something bad on your comp thats messing everything up. But don't throw away your computer, since that would be like junking your car because some asshat put sugar into the gastank.