How do I fix mentioned Issue (Windows XP SP2)

Can some one have face following issue with their Windows XP SP2 PC.

“When double click on local disk (C,D,E) Open with prigram will come Open With”
But it suppose to be explore the locak disk. I have noticed after right click on local disk there is addition propertise “Auto Open”. some bugs or virus have changed the system registry.
Can some one advise me how to fix this Problem.
Thanks
Forhad