Using a Dell Latitude E6500. DxDiag.txt Sound tab reports:

Description: Speakers / Headphones (IDT High Definition Audio CODEC)
Default Sound Playback: Yes
Default Voice Playback: Yes
Hardware ID: HDAUDIO\FUNC_01&VEN_111D&DEV_76B2&SUBSYS_1028024F&REV_1003
Manufacturer ID: 1
Product ID: 100
Type: WDM
Driver Name: stwrt.sys
Driver Version: 6.10.6227.0000 (English)
Driver Attributes: Final Retail
WHQL Logo'd: Yes
Date and Size: 7/31/2009 19:16:12, 409088 bytes
Other Files:
Driver Provider: IDT
HW Accel Level: Basic
Cap Flags: 0xF1F
Min/Max Sample Rate: 100, 200000
Static/Strm HW Mix Bufs: 1, 0
Static/Strm HW 3D Bufs: 0, 0
HW Memory: 0
Voice Management: No
EAX(tm) 2.0 Listen/Src: No, No
I3DL2(tm) Listen/Src: No, No
Sensaura(tm) ZoomFX(tm): No

I tried both sound drivers available in the drop down. The Vista sound driver and the WAV driver. Muted and unmuted the laptop several times and raised and lowered the volume several times. Both in-game volumes are set to max. Other PC and game sounds play fine.

Try setting your sound to stereo in Windows if it isn't already. If you can post your waverror.log file (located where you installed Vendetta Online) that will also help determine the problem.
If setting your sound to stereo mode works, this is a known problem that we are working on.

It's definitely stereo mode. I should probably mention it's windows 7.

waveerror.log:

Windows Sound (WAV) driver
wavoutcaps:
Manufacturer ID: 1
Product ID: 100
Driver Version: 6.1
Product Name: Speakers / Headphones (IDT High
Formats: 0xfffff
11.025 kHz, Mono, 8-bit
11.025 kHz, Stereo, 8-bit
11.025 kHz, Mono, 16-bit
11.025 kHz, Stereo, 16-bit
22.05 kHz, Mono, 8-bit
22.05 kHz, Stereo, 8-bit
22.05 kHz, Mono, 16-bit
22.05 kHz, Stereo, 16-bit
44.1 kHz, Mono, 8-bit
44.1 kHz, Stereo, 8-bit
44.1 kHz, Mono, 16-bit
44.1 kHz, Stereo, 16-bit
Num Channels: 2
Support: 0x002c: WAVECAPS_VOLUME WAVECAPS_LRVOLUME WAVECAPS_SAMPLEACCURATE
[03/11/11 09:22:09] Initializing DirectSound...
44100 Hz 16bit stereo
[03/11/11 09:22:09] DirectSound Initialized.

I am having a very similar problem with a Dell laptop and the same audio chipset. I am looking forward to a resolution... I tried every different combination of settings I can think of and nothing is allowing the game to recognize the sound card.

Had the same problem. Running Win7 64 bit. Using G930 Headset. Solved it by running Vendetta in compatibility mode for Vista SP2. Good luck and hope this helps you...