I have a locked administrator account. Other accounts are unlocked, but they have no rights. I want to get a password from the locked account, or maybe password hash, if possible.
If you have no rights at all, then you are out of luck. There is no way to retrieve the password. Depending on the operating system you can reset the passwords in different ways:
For windows you will need to reboot the machine and use a special CD to try and reset the password. One tool you can use is this one: http://pogostick.net/~pnh/ntpasswd/bootdisk.html
On Linux you need to boot with a live CD, mount the hard drive and generate a new hash for the root password on the live cd using passwd. Then go to you /etc/shadow and copy that hash for your root account to the /etc/shadow on the mounted hard drive. When you reboot your machine the password will be the password you generated on the live cd.
Windows stores passwords with non reversible encryption, but you can try two things, both with Windows boot disks (which bypass your permissions problems by loading their OS's and mounting your C:\ Drive). First, you could run a program like Ophcrack to try and challenge their NLTM hashes. This will work if they have a weak password, but a dictionary attack can only get you so far. If it does work it will return a plaintext password. Alternately you can just change the password (I like to use the HBCD, which has the added advantage of being an AV boot disk, and can work on Linux and Windows).