Can you tell us what system you are running? Also the fan issue was on later models, so I'd like to be sure we know your exact machine. The serial number is on the bottom of the stand, please go here and plug it in and tell us what you have: https://everymac.com/ultimate-mac-lookup...
Now that you have the Snow Leopard install disk, reboot with the disk in and hold down the C key. Go to the second page of the installation where the pull down menus appear. Go to Utilities > Change Password and change the password.
In the same way you got to the password change, go to Disk Utilities and run it. The repair partition is on much later systems. Personally I would also use Disk Utilities to a Secure reformat and erase of the drive using the write 0's option to map out any bad blocks. Format it GUID and Mac OS X Extended, then install the system and set up your user account.