Since I installed vegas every game i own ,which ranges from command and conquer to dragon age origins about 15 games in all, crashes within 1min 40 seconds, it never makes it past that amount of time. Before installing vegas i've never had a game crash, Every game crashes the same way with a graphical screen freeze and the occasional audio loop, this causes me to have to restart my computer, but all my games are now unplayable.

Anyone know how to fix this, please.

Sounds like a common file issue, maybe DirectX? start with dxdiag, see if it finds anything out of place

Uninstall steam and see if the crashing goes away.

Tried it, I just reformatted last night and just reinstalled most of my games and Im still having the same crashing problems.

Very well could be something hardware or software related then. Check to make sure you're using stable driver sets, and then start checking hardware to see if it's failing.

did you reload your other games and try them before installing & loading FNV again?