Don't install it in Program Files and see these threads for the tweaks needed to get it to run
http://www.gamesas.com/topic/1454296-falloutlauncherexe-wont-run-on-windows-8/
http://www.gamesas.com/topic/1451540-any-way-to-stabilize-fallout-3-on-windows-8/
http://www.gamesas.com/topic/1448428-fallout3-stable-on-win7-64/
The issues for 7 and 8 are the same.