Skype vulnerability?

This computer is making me paranoid.

Same day I booted it up, after I got a message stating Windows failed to start with a detail of "Harddrive = 0", I surf the web and Skype out on it's own starts up. I even checked the settings and the "Start when Windows starts" was still unchecked. Even though everything seems fine, I get the feeling a dormant program got installed without me knowing.

I'm using Norton for protection.

Get rid of Norton and use MSE.

Microsoft Security Essentials - Free Antivirus for Windows

Next thing to do is run full scans of malware, spyware, and adware software and for anti-virus for any malicious bugs and virus