I have wondering since

1. Their symbol is on the atom bomb in Megaton

and

2. Since all the Vaults were used for experiments, wouldn't it make sense for them to set off an atomic blast to get their experiments started?

I doubt it, why would they obliterate their own HQ, and if they did, where would they monitor it from?

I found it a bit odd that the atomic bomb in Megaton had the Vaul-Tec logo on it. Would make more sense if it was made by West-Tek (who seem to be the primary military contractor in the Fallout world). I did always feel like the Enclave started the war by nuking the West-Tek FEV facility.

It's not Vault-Tec symbol. It's a bit similar, but if you look closely, it's not the same.

The ACE computer in F2 says that Artificial Intellegence computers became bored and began to effect the world around them.

This could mean that a Comptuer launched the first nuclear bomb.

but if thats the case, then somehow the U.S. and/or maybe even China was helping to cover up the fact that a computer launched the bomb. which doesnt make any damn sense.

or maybe that was sarcasm...?

You got a pic handy of it?