in my case running NV in windowd mod doesnt fix anything

Well, the system requirements call for a Dual Core 2.0 GHz processor. If you have a single core, you don't even meet that.

I had a very similar, almost exact problem as the OP described, however it would only affect certain areas of the game. Namely Vinny and Vance Casino and South Freeside. In particular with V&V Casino, subtitles and speech animation would work but no audio was playing and after every paragraph I'd need to press escape for the next one to be initiated by the NPC.

Also the NPC's and my PC would not sit correctly in the area too. Whilst my PC would sit towards the Coin slots, the NPC's wouldnt and it would look like they were floating in air. Again I would have to press escape to remove myself from chair I sat on.

I have an SB Audigy X-Fi as my main soundcard. Firstly I turned my Hardware Acceleration to Basic, which "did" solve the no audio problem and the sitting animation. However doing so caused instability in sounds in other areas, namely Helios One where after err "doing" some things there, would cause the sound to become corrupted and screechy. Secondly, as a test I decided to disable my SB card and enabled the onboard Realtek HD. Fortuneatly this did solve all my particular issues the the sound in the game, testing V&V, Freeside and Helios One, which all worked flawlessly after the Sound Card change.

I know this solution is not always available to everyone and in fact some SB cards have no problem at all with the game(my brother has an old SB Live24 card and works fine.) However I would suggest for now trying to change Hardware Acceleration to Basic and see where it goes from there.

I have had these sound issues as well i am going to try if running it in windowed helps but i havent had any freezing problems

ok it worked beautifully as i started again but it started going down hill once i got outside first with the the gun fire then people talking and at that point i just quit and came back to report that it only works for maybe ten minutes or maybe in small areas we need an up date or something that can help bethesda

Apply this patch first... It should work
http://www.theplatform.info/user/mateibota/view/fallout:-new-vegas-sound-delay
Steam users, the unzip path is more like C:\Program Files\Steam\steamapps\common\fallout new vegas

If that doesn't work. Start the game and then Alt+Tab. Ctrl+Alt+Del and go to processes. Set New Vegas to 'High' In priorities.

Amazing, but this really works. Fixed all the issues for me.