Sound like you may have some form of infection on your laptop.
Would suggest that you run any malware programmes you may have, and see if that/they finds anything. Perhaps run ADWCleaner or a similar program. At present I am using a beta version of Malwarebytes Anti-Root Kit with good success rating.
I run Firefox, Chrome and IE on a vista laptop without problems. I select the default browser to use, and not the laptop by un-ticking the relevant boxes requesting default.