I think I have a virus on my computer. Every time I try to install something, my computer removes it after restarting, especially any security program. I dare not mess with my registry or anything unless I'm sure of what I'm doing, and at this point, I'm not. I also have a problem uninstalling StopZilla. I've reinstalled then tried to uninstall, but after restarting, it is still a dupe sitting there, not working. Any ideas to solve these problems?

I'm running a Vista 32bit on a laptop. I have no real defense except for windows defender (which really does nothing).