It seem that internet explorer has gone corrupt on this computer,
Please follow these instructions.
1. Rest your internet explorer.
http://support.microsoft.com/kb/923737
2. Restart your computer in the safe mode with networking.
how to restart the computer in the safe mode with networking:
As soon as you restart the computer start hitting F8 and by using up and down arrow key on the keyboard, choose safe mode with networking and hit enter and hit enter again. Then you will reach to desktop.
Now, launch internet explorer and scan your computer with malwarebytes:
http://www.malwarebytes.org/
Now, restart the computer.
This would fix the problem.
Also download Mozilla firefox as an alternative browser in the safe mode itself.
http://www.mozilla.com/en-US/