XP Internet Options Security Zone “My Computer” as “Restricted site”

in my laptop, in security tab of internet options only one site is visible ie “My Computers” and it is marked as “restricted site”
Am not able to download any software including IE7 and or DLLs or load any third party SW.

How can I chnage this? What should be done to make other four levels visible in security zone?
And how to remove “My Computer” from restricted zone? Please help!!!