Assuming you have onboard audio and not one of the Creative card options you use a Realtek HD driver.
Since it is not loading, but audio devices are showing up in Device Manager with yellow flags it really sounds like the driver is not correctly loading.
I would uninstall any Realtek drivers for audio (you also have them for your LAN; leave that alone) you find.
Then I would download and install the latest 64-bit Win7 driver from Realtek
. If it fails to load the sound chip may have failed (usually you would either get a red flag or the audio just would not show up in that situation). May need to add a sound card or USB dongle replacement.http://www.dell.com/support/drivers/us/ ... t/xps-8500
You have pretty much done what is on my checklist:
Run MS' Fix-It.http://support.microsoft.com/mats/AudioPlayback/
If that doesn't work, for Windows OS (but note Vista/Win7 limitation below):
1. Make sure volume is not turned low or muted at the operating system level. Make sure the speaker's volume isn't turned too low or off on any speaker manual volume control.
Test the front and back audio port with known working headphones to confirm it is the sound and not the port that is malfunctioning -- since by using two sources (that hopefully one is confirmed working) you have confirmed it isn't your speakers that have ceased working.
Try with more than one type of media/media source to rule that out as the problem.
If it is the port then you can look in the BIOS to make sure it somehow wasn't disabled (unlikely). Otherwise the port is probably defective. Choices are to switch to a working port, or add a soundcard or sound USB fob.
Also, if you use a soundcard make sure you are plugged into the soundcard's port and not the motherboard's (onboard audio) port (which would be disabled in BIOS).
2. Check Window's device manager for yellow or red flags on audio. Install an up to date audio device driver. If you use a card it is possible that removing the card, rebooting, reinstalling the card and rebooting will allow the OS to select a correct audio driver to get it functioning.
No yellow/red flags in Device Manager?
No Problem Devices listed in MSINFO32 (System Information in Win7) under the Component tab?
But unless the driver was somehow corrupted (also unlikely unless you installed some app right before the audio failed)--in which case either rollback the driver or better yet install the latest audio driver. Otherwise the audio chip has failed; solution add a soundcard or sound USB fob.http://pcsupport.about.com/od/windows7/ ... dows-7.htm
You can get the last driver available for your PC from either the PC vendor's support download page, or the motherboard vendor's (in a custom built) support download page. The newest drivers are available from the maker of your system's audio chip.
Audio Driver vendors: There are two categories of audio drivers put out by a audio chip vendors: older AC'97 audio driver and the newer HD (High Definition) audio driver. You must know which one of them your system uses. As far as I know ALL drivers from any chip maker in one of the above two categories work on all of their chips from that category.
Analog Devices ADI = Soundmax (Intel)
Realtekhttp://www.realtek.com.tw/downloads/dow ... l=3&Conn=2
IDT [SigmaTel] (Intel)
Creative Soundblasterhttp://support.creative.com/Products/Pr ... px?catid=1
3. Check BIOS that onboard audio is not set to disabled IF you use onboard audio. [If you use a soundcard, remove it and switch to onboard audio at least temporarily.]
4. Run dxdiag in run box. There is a Sound tab. But while there also check msinfo (aka msinfo32) found in last Tab ("More Help")...look at the problem devices category in Components > ProblemDevices. [Unfortunately dxdiag's testing has been crippled in Vista/Win7.]http://support.microsoft.com/kb/190900
[XP]http://windows.microsoft.com/en-US/wind ... th-DirectXhttp://windows.microsoft.com/en-us/wind ... ostic-Toolhttp://support.microsoft.com/kb/308549
3rd Party free audio testing app (Passmark Soundcheck)http://www.passmark.com/products/soundcheck.htm
5. Finally if you actually have a sound card, you can remove it and test the audio from your onboard chip. May require BIOS setting change. May require updating the motherboard's audio driver. Obviously if it works and you replaced the correct soundcard driver, this is pretty good evidence the soundcard is dead. You can move the soundcard to another slot if available to rue out that slot. Also sometimes the mere act of puling a card and polishing the contacts on the card gently with a pencil eraser to remove any oxidation will restore its functioning. If it is onboard audio that is shot replace it with a cheap PCI card or USB dongle---note when MB components start to fail it is usually a sign other MB components are going to fail so don't put a lot of money into it.
If onboard audio does not work I would RMA the MB, either with the vendor if your time has not elapsed and the MB mfg. if still under warranty. [many MB's have 3 year warranties so check]http://windows.microsoft.com/en-us/wind ... in-windowshttp://www.techspot.com/community/topic ... ms.160964/http://h10025.www1.hp.com/ewfrf/wc/docu ... =c00833257
If you need cheap, reliable and easy quality replacements for the sound (choice of colors; just plug into USB2 port):http://www.newegg.com/Product/Productco ... 29-128-002
If you need cheap and reliable quality replacements for the speakers:http://www.newegg.com/Product/Productco ... 36-121-013