My administrator’s username or password won't unlock or install??

Yesterday my hard drive crashed. I still had my older drive from my previous mac so I took the fried one out and put the old one in. After installing snow leopard, everything works fine, except an odd problem. I can use the administrator’s name and password to log on to the computer but trying to unlock a system preference page doesn't work. Also the prompt that comes with installing software doesn't accpet my username or password. I've reset them both in system preferences and in single user mode. I've used command R and typed resetpassword in the terminal and tried everything. Is this problem due to the old HD? Any advice would be greatly appreciated, I can't install anything or make changes to my computer.

And I tried resetting my permissions but I still get the prompt to enter my username and password. What's odd is that isn't the username usually autofilled in these prompts? And if both worked on the first login page to open my computer why won't they work any where else on my computer? I've search everywhere for this problem but I haven't anything that addresses exactly what's happening here.

Is this problem due to the old HD? Any advice would be greatly appreciated, I can't install anything or make changes to my computer.

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Did you wipe the old hard drive clean and reformat it before using it or did you just install Snow Leopard over what was on the drive?

I did wipe the old drive clean, but when I first started it after the install, it had preserved the old username and log in from the old drive, which I had remembered.

If it preserved the old user name and login, then you didn't wipe the drive clean. The permissions and ownership are definitely messed up on that drive. Try doing a right click on your drive, get info, and check the permissions. You may have to wipe it again with Disk Utility from your Snow Leopard DVD and maybe do a one pass zero write over the entire drive.

I did check the info on the drive and under sharing & permissions it does say: You can only read. Next to system's privilege it says Read & Write, then Wheel: Read Only and everyone: Read only. I no longer have the start up disk, they are 5 hours away at my parents house, if they are even still there. I can't unlock the permissions because it prompts me again for the username and password. I've tried using the info for the old drive, for the current computer's and for the newly undated password that allows to login, but nothing works. Is there anything I can do without the OS X CDs?