You could have inadvertently installed some sort of toolbar, that will need identifying and removing

You could have inadvertently installed some sort of toolbar, that will need identifying and removing, or it could be some malware problem, have a look at

searches are redirected to another site
after you read that try to explain what searches are redirecting, and if possible follow the advice it contains

is malware the cause of my firefox problem
the fact the problem is on both IE and Firefox could point to it being related to your ISP or malware external to the browsers.

Cannot remove an add-on (extension or theme)

Post back with how you get on.