Access to Extended Stored Procedures

Hi,

How can I remove access to extended (xp_) stored procedures?
Is there any revoke on <stored_procedure_name> ... command? How can I generate a script of all users who have execute privileges for these procedures? Also, is there any way of restricting (instead of removing) access to those procedures?

Any help will be greatly appreciated!!!
Thanks,
Allarevoke execute on xp_fixeddrives from public|||Thanks! Also, how can I review which stored procedures public has execute privileges for?

Thanks in advance!