Please understand the following:
If you are not the owner of this computer this may constitute a violation of your company's policies. You must clarify the situation for us before we can help you any further. Lack of clarification means we cannot help. If you operate the domain and the network this is quite different from using a 3rd party system that you do not own. The ability to provide information is different and the consequences you could suffer from bypassing security on a network, albeit not secured, is not our responsibility as forum administrators or moderators.
Further, enforcement of group policy over the domain network would rightfully prevent you from accessing the local administrator account on your computer irregardless of if you use a offline password changer. This is because you are not authorized to access these local system resources due to controls set in place by the owners and administrators of this network.
Your post does not read as if you have participated in the administration or implementation of this Windows domain network. This seems to indicate that you are trying to bypass a security policy and protocol that has been put in place by a third party which may own the computer you are using or control access to network resources.
If this is the case, you must consult with your IT or MIS Department to resolve this issue. If it is not the case, your entire network has been hijacked and you do not know what you are doing. The latter is very unlikely. Please consider that a compliment in good taste. However, it really comes down to whether or not you have authority to make these changes. You should consult with the management of the network you are on to better understand their security policies rather than try to override them using this forum.