I am probably being paranoid, but let's assume I'm not. I think someone has breached my pc

How do I know for certain? My settings constantly change and my mouse cursor acts as though it has a mind of its own. I received the computer as a gift from a former boyfriend. He works for a relatively large company for the area we live in and has his own systems administrator at work. A computer whiz from what I understand. My ex is the VP of the company. He brought over some software to download on my new pc that I didhn't have. He could have tampered with my pc or made it somehow accesible from his work? I really don't know much about computers other than from a user persepctive. Any ideas? Other things happen to, as my history show sites that I have never accessed.

I am probably being paranoid, but let's assume I'm not. I think someone has breached my pc security?auto protect

First go to windows.com and have a dianogstic done and see if you have all you security upgrades...also go to limewire and borrow from someone else a computer forensics program that will be able to tell you all breaching and attempted breaching activity...last but not least create a safety restore point...a period in time prior to its acting up and restore to that date. If you do the system restore you will loose no data. Also check and see if you have a pop up blocker and make sure it is enabled cause if not some of the extra sites in history could be from that. Hope this all helps some.

I am probably being paranoid, but let's assume I'm not. I think someone has breached my pc security?downloads

There may be something on ur computer but ur spyware blocker has not detected it because it uses a special thing called a "rootkit" to hide it on ur computer.
Does the same things happen, when you are disconnected from the internet? It's possible that you have some spyware, that isn't detected by software, but if you don't keep any important informaton, it's nothing to worry about. At last you can always format your hard drive and reinstall OS.