I cant found my windows Media Center in my PC with window vista ultimate OS.?

WMP or WMC is no where to be found in my system even if I go through start ,program.If I try to open a file a file in my E-mail with WMC,it says``windows cannot open this program because it has been prevented by a software restriction policy.For more information contact your system administrator.What do I do to rectify this problem?Please help me out.