Help im out of ideas

Hi, im trying to gain administrative rights on a network, i have tried the following but it hasn't worked.

1.Cain and abel (wont let me view the domain users says i dont have permission, i think the admin has used it so basicaly it does nothing, apart from tell me mac addresses but no passwords)

2.I tried using windows server 2003 admin software, i needed to be admin (that was kinda a given but i thought what the hell lol).

3.I tried using getting remote sams and importing them into ophcrack, couldn't find any remote sams.

4.Keylogged but local admin password is different for every machine and not the same as the network admin password.

Im out of ideas please help me (im fairly new to this so if i need to read/learn something im willing to)

Open Cain and Abel go: ->Sniffer ->Click the white area then the the plus ->Scan Subnet ->Click APR at bottom ->Click the white box and then plus ->Choose which pc you want to monitor ->Wait until the pc inserts a password you can use for better rights which you can see in the passwords field.

Thank you