the system administrator has set policies to prevent this installation

when installing itunes on mums sony vaio with vista home edition. a message saying "the system administrator has set policies to prevent this installation" pops up not allowing the installation to continue. had a quick look on other forums and the general concensus is that the settings that need changing are deep in the technical parts of the computer which im not prepared to go to. has anyone else had any problems like this and is there an easy way to fix it!?