Hey Everyone,

I was just curious if it is possible to have possitive reputations with the NCR and the Brotherhood of Steel. I just found Vault 3 and know that there are quests with both factions and I don't want to screw over myself later in the game with either faction. I have a positive karma character and so I do not care if I anger the Khans, Fiends, or Legion. I just want to try to stay on good terms with the NCR and BoS. Can you do both quests associated with each faction for Vault 3 or do you have to choose one or the other? Thanks!

Nope, you can buddy up with both of them.

The two quests really involved in Vault 3 are to kill Motor-Runner for the NCR[unmarked] and deliver some drugs for the Great Khans. Just do the Khans quest first.
The brotherhood of steel quest is simply to retrieve some components, assuming you pass the speech check to enter peacefully, there is nothing stopping you from getting the parts without blood shed.
Save outside Vault 3, tell your companions to wait as they may open fire and blow it. And put on any speech boosting gear if you have it.

*punch*
Don't listen to people like this, yes you can, it's a bit easy though.

EDIT: I've been ninjad.

Actually it is true. If your siding with the NCR there's a mission where you can actually make the BOS allies with the NCR but with a hit to your NCR's reputation.

Save to a different file before entering Vault 3 trust me you don't wanna lose your file to save corruption. I haven't had it happen but you dont wanna take that risk. As for your question yes its entirely possible to be friendly with both the BOS and the NCR. I'm only friendly with the NCR because I wanna screw them over later hence my sig "The House Always Wins".

I miss read the post, I thought he said "can't"

*unpunch*

Listen to people like this, you still can and its still easy.

Think about buddying up with Veronica while finding the BoS and it might even be easier...

If I am a good character, will doing the mission for the Great Khans and Fiends give me bad Karma since technically they are "evil" groups?

Also, once I do the quests (marked and unmarked) for the Khans, NCS, and BoS, can I just kill the fiends for the XP and loot them, or since I passed the speech check and they do not see me as an enemy, will that give me bad Karma?

*edit* - never mind, I am guessing I have to kill them anyway for the NCS quest, right?

It won't grant bad Karma and really I wouldn't call the Great Khans evil. There actually kind of noble in there own way.
The NCR quest is unmarked and all you do is break Motorunners helmet to Colonel Hsu. For the Khans you simply give hm a package.[but you need to finish the khan quest before killing Motor runner]. But due to a bug the helmet isn't actually removed but is weightless anyway. [despite what it says].

If your an unarmed character you'll want to do the khan quest.