I have been playing Fallout NV since it came out, with many mods and everything is fine. I have played without mods, reinstalling it, everything, and there is no sound, sound plays on the launcher, but not on the actual game.

The game worked fine up until one launch when the sound suddenly stopped. I hadnt changed any drivers or setting e.t.c.

I have tried changing other options such as, reinstalling, no mods, windowed mode, compatibility mods, 2.1 speaker config.

I have a Creative SB X-Fi soundcard, sound works fine on other games, and desktop.

My system are:
Windows 7 Home premium 64 bit.
ATI 4870 512mb
4gb RAM
AMD Phenom II X4 3.2ghz

any help would be much appreciated.

My system is pretty similar. I have no sound issues. Have you tried ALchemy?

Can you link me, what is this?

Alchemy should not be needed to get sound. It simply adds the hardware acceleration back to the sound card. (W7/Vista did things differently that XP and removed hardware acceleration.<_< )

Did you try reinstalling the sound drivers? You mention the game but not the drivers. That's where I would start.

Do you have any software installed that was made by ArcSoft?

Common examples are "Total Media" installed for TV card applications and "Media Impressions" installed for some scanners.

Arcsoft installs codecs that can cause the sound to be lost in FNV.

One solution is to uninstall any ArcSoft applications.

The other solution is to rename the ArcSoft codec that causes the problem. Search for the file "asaudio.ax", you may find it in the system32 folder and/or the sysWOW64 folder. Re-name it to "asaudio.ax.bak". Your ArcSoft applications may stop working or may continue to work as usual.