Security Help

Hello,

I recently have noticed some minor performance issuses witth a new computer and and odd changes.

I have windows vista and when i log out and come back the next day i come to the message Incorrect Password(well basically the thing vista prompts you with after incorrect login) when i left it on lgoin screen. Also recently after waking my computer up from sleep mode i came to a ie screen that i never navigated to nor had anyone else and my computer was running surprisningly slow until i rebooted. Things like this start to worry me because they are not normal i have run multiple scans with internet security and find nothing but i am not completely convinced. If i need to post any system specs, running processes, services, etc. or suspected programs that may grant access please state that in this post. I really dont want to have all this security trouble and usually dont but i just wan to make sure I am safe.

Thanks