Hi, I am planning to build a computer. I never built one before.

I know what it looks like inside a typical mid-tower casing, BUT the casing I have is from a "Olivetti Personal Computer M240" computer (a mid 1980's computer), I have difficulty planning the right hardware for this particular casing. The biggest QUESTION I have is how do I fit a motherboard in it correctly since this is a REALLY old computer. 

This is the computer casing I am trying to use. I already clean out all the old hardware out of it, now I want to put hardware that is compatible with Windows XP Media Center Edition Operating SYSTEM in this case. Could anyone tell me where do I start?
you will need to do a LOT of modifying to that case to get it to accept modern hardware and as we are not physically there, we really cannot give you any instructions on how to modify it. you will need to use your better judgment and experience. however, if you are not experienced with computer hardware, i highly suggest that you do not start modifying the case. I KNEW I would modify it first since the modern hardware seems so different to this computers hardware . I thought I should use a modern Case first but since I had this computer that has booting problems, and is not compatible with today's hardware I thought I would use it's case instead. Since I have no experience building computers I'll get a modern case. Thanks