Server 2008 R2 windows time

I'm trying to set the PDC with an external time server (from my ISP) but in the command prompt when I type in:

w32tm /register

W32tm /config /manualpeerlist:""

W32tm /config /reliable:yes

W32tm /config /update

Net stop w32time

Net start w32time

But I always get "The following error occured: Access is denied. (0x8007005)

I tried to do the net stop w32time
and it gives the same access denied error.
I tried to do net start w32time and same error.

I went to the services.msc and windows time is set to automatic start but it is not running.
I go to start it and it gives the error
"windows could not start the windows time service on local computer" so I tried to log it in under the domain admin account… Same message.

Does anyone have any ideas?

Thanks!