Reinstall MacOS 10.7 Lion on Macbook A1181 Problem

Hello,

I have an urgent problem to be solved, if you can do it, pretty please. I have received as payment, an old Macbook A1181, mid 2007, with 3gb RAM in plus of its basic configuration. It camed with Lion 10.7 on it, but full of old files, settings, and with a user account of the old owner. This night, JUST before I will give it as a gift further to my girlfriend, I wanted to erase it and restore it back to its factory settings. I saw a few films on youtube on how to do it without disk. I have read on Apple forum the instruction and everything looked easy. I started, and now at the Reinstall Mac OS X step, after verification, it ask me for the credentials of Apple account who bought the Lion Upgrade. I called at the guy who gaved me the notebook to ask him if can do something about it, or just give me the credentials for few seconds. And his answer was that the Lion I had on the notebook wasnt official, it was just tooked from the internet and he doesnt know nothing about what can I do now.

My problem now is I have a Macbook stucked in the Mac OS X Utilities screen, and I dont know what to do. I would like to buy the upgrade, but I dont know if it works if the notebook still thinks I have Lion, and I just want to reinstall it. Also I have pressed option(ALT)+command+ R during boot, and I dont see the screen where I could buy the upgrade. In the app store on others PC I see i can buy it, but it comes in 1-3 days even if i just buy it online and i need it in my account to show as bought.

What can I do in this moment? How do I do a roll-back at least at an older version of OS X ? A fast and good answer will be very thanked. I am worried, and in a hurry. Thank you.