What do I need to know and do to restore computer?

I was given a hp desktop, the sticker says Windows ME, serial # 4503408596, HW BOM 101-SW BOM 89, 15291703408596, SY-P2917A
those are all the numbers I see on desktop...The monitor is a Envision. I just don't know how to began to get it up and running, can someone help me? I think I need to buy a windows me restore disc to put it back to factory settings, but where can I buy one if that is the case.

Just go buy a Windows XP disc, so you can upgrade. If you upgrade a certain way, you can wipe the computer and start fresh in XP. Here's what the box looks like:
http://tinyurl.com/y2859pd