My family recently purchased an Optiplex 790 bundle from a neighbor that closed down her dental office. The computers were setup by an IT Specialist and were networked together. I wasn't the first to get around to it but apparently instead of immediately attempting to system restore the computer User Accounts were DELETED via the Control Panel. The computer no longer has any actual accounts and merely has one user on the start up screen which I assume is the default user created on the domain. As this was a secondhand purchase, I do not have the original copy of Windows 7 Professional to restore to factory settings AND cannot execute a system restore as I do not have administrative rights. I have tried everything from using the cmd prompt, creating new user accounts (cannot be found on the operating system), granting the mysterious user account administrative rights (requires admin rights), or booting in safe mode and creating new accounts or unlocking the super admin account (receives System Error 5). I have also tried F8 upon startup and it appears as if the Specialist has disabled an advanced System Restore from there as well. I'd really not like to have to replace the OS completely.... I have the product key and it is verified. Options? Opinions?