Administrator Rights

Hi, I have a question which has been discussed before, but mine puts a new
spin on it.
Being the sole account on Vista I am an admistrator with all access rights.
However, when i wanted to load just a simple BT broadband security sofware
disk, it came up with the usual "You don't have admistrator rights...".
This was addressed earlier in the newsgroup and people were advised to right
click and choose run as an administrator.
But get this, I created a new account with administrator rights and this
account is allowed to run the disk.
What can I do to my original account to make it run the disk.

Chris