Unable to reinstall Mac OSX without an Apple ID that I don't know I was recently given a retired MacBook pro from my work.  It's a 2009 A1278, originally shipped With OSX Leopard 10.5.7.  When I try to reinstall, it asks me for an Apple ID.  Nobody around the office recalls what that might be, since it was 8 years ago when it was originally purchased, and the records from that time were messy at best, and we've gone through a substantial management change since then as well.

I'm considering buying a new install disk from Apple, but they don't seem to sell 10.5.7.  So my main questions are, how do I get around this requirement to enter the Apple ID and re-install the OS, and if I purchase a disk that's a higher version than what was factory installed, will I be able to install it?

Any other details you have would be appreciated.  I just want to make this thing compute again.  

Thanks!
You can put up to macOS 10.11 Yosemite on that Mac. 

If you have Macs at work see if you can download a copy of it there or from a friend. I have also heard that an Apple genius can help with that at an Apple Store as macOS is free toinstall on any Mac. 

Once you have downloaded the OS create a bootable USB key. DiskmakerX will make one for you, there is also a terminal command that you can use to do the same thing.

If you boot from installable media and then wipe the drive before proceeding with the installation that problem with an AppleID will go away and you will be free to register the OS under your own AppleID