2008 IMac restore

[aloum]

I have a 2008 IMac that boots into windows 7 Enterprise. I bought it used and don't know the password. I have tried so many things to reset the windows password but no luck, because it was linked to a domain and the both the Admin and the Administrator accounts are disabled.
I went to restore it but, I get an error; saying "mountain lion is unavailable try again later", restoring from timemachine keep searching for backup for hours. I want to know if it is possible to format the hard drive and start from scratch? If so, can I put El Capitain and how do I get a copy and what are the steps to format the drive?
I appreciate any help.

 

[Phil in ocala]

Let me make an obvious reply...go back to the person who sold it to you and get the password....you never should have bought it without the password in the first place.

 

[aloum]

Thanks dude, very valid, but I want to see if there are other options like the ones I asked about in my post.

 

[Fishrrman]

Buy a Snow Leopard install DVD, boot the iMac from the DVD, reinitialize the internal drive to HFS+, install a fresh copy of OS 10.6 onto it, then upgrade as desired...

 

[aloum]

Thank you for your help.