Help! Virus problem?

Hello! I have no clue what is going on with my computer. It is a windows xp and lately internet explorer is 'locked down'.

When I try to exit out of the internet explorer, it says there is an error. Rebooting the computer doesn't even help. If I shut it down all the way and turn it back on, the internet explorer is there refusing me to get off. I can't do anything on the open screen of internet explorer. I can open a new internet explorer (like I am now) and go online and even exit. Yet it won't exit on the others.

Please help!