I just payed 20$ for the fallout 3 game of the year edition on steam, and when it finished downloading, the launch screen started up immediately.... but when I clicked play, the launcher disappears, and absolutely nothing happens.... when I find the original .exe file it gives me some [censored] about a missing file.... I'm new to this forum stuff so any help would be great!

One file does not validate, that is normal, ignore that.

As for the other issues, see this as you may have the game installed in the wrong place, and some tweaks need to be made once it is installed in the right directory

http://www.gamesas.com/topic/1465357-installing-fallout-3-with-windows-78-and-xp/

....... this one from steam, that I purchased, download's directly.... I can't choose where It goes