How do I know if a case is ATX form factor?

I recently moved into a new apartment. The previous tenants left behind an old, full-tower server case in a back closet. It's heavy, metal, and about 3.5' tall... Oh, and it looks like it was spray painted blue... How do I figure out the form factor on an old case like that (short of just putting a board in and seeing if it goes). I'm thinking (just as the original owners probably were) that it would make a fairly kewl new PC (lots of room to work with (should making cooling easier). If it had a power supply in it, then I'd know what it was... I could not find any identifying markings anywhere on the case.How do I know if a case is ATX form factor?
take it to the shop you plan to get the motherboard from and get them to identify the anchor points against a board, or, if you know someone with an old mobo in their closet, grab it and sit it on the anchor points to see if it lines up.





chances are it will just fit, but it is kind of a huge case so probably worth checking first.