Cant download skype on vista home premium?

was away from home 6 weeks,came back and machine had been switched off somehow and windows had updated it ,as screen icons where larger and spaced apart,,also skype was gone,,now wont let me download skype again,,message reads..(.the installer has insufficient privileges to access the directory c;\program files\skype\plugin manager\mls the installation cannot continue log on as administrator or contact your system administrator).....i am the administrator and have to sign in with a password but am not given any direction on where and how to log in on that screen,,,also a little later after that screen appeared i got another massage saying....(run Dll-error loading c;\program files\registry mechanic\updateHlpr.dll.)...whats that about,,would like an urgent reply if poss. rgds