Sumit, here is a great article that should help you out:
http://infosecuritymag.techtarget.com/articles/february01/cover.shtml (It's a
bit dated but the information in there is good.) Be sure and read the
paragraph entitled "P2P Action Items."
In our organization, all of our users have "Domain Users" rights only AND we
have IE Downloading disabled. If they were able to obtain the executable they
would still need Admin rights to install the program. Additionally, the
"Security" tab in I.E. is not visible. Anytime a user requires access to a
specific site to download work related material, we add the legitimate URL to
their "Trusted Sites" list. We are currently working to distribute a global
"Trusted Sites" list to ease the overhead on administrative tasks.
Hope this helps,
Eugenio