Hi,
A new sound card may work IF there are not other issues including BIOS, low level chipset drivers,
and other major device drivers.
Since you upgraded to Windows 7 did you run the Upgrade Advisor and check with the Compatibility
Center (for device compatibility)?
Windows 7 Upgrade Advisor <-- please run this nowhttp://www.microsoft.com/windows/windows-7/get/upgrade-advisor.aspx
Also check the Compatibility Center (for device compatibility)?
http://www.microsoft.com/windows/compatibility/windows-7/en-us/default.aspx
Check with the System and Device makers for updated drivers and many have special instructions
to help with upgrading to Windows 7. Many have specific instructions for upgrading so be sure to check
with their Support, on-line documentation and Forums.
========================
If the system is Windows 7 compatible AND there are drivers for your sound (and other devices).References to Vista also apply to Windows.
Fixing a customer problem: “No Audio Device is Installed” when launching sndvol on Windows Vista
Also update or re-install the driver.
Control Panel - Device Manager - SOUNDS - look for HD Audio - Mine says RealTek High
Definition Audio (that is an example and yours may have an entirely different name/maker).
Write down description make and model - double click on it - drivers tab - write down version.
Now Click UPdate Drivers which may not do anything as MS is far behind certifying drivers.
Then RIGHT CLICK on it and UNINSTALL - REBOOT - this will rebuild the driver stack.
1st go to system maker's site and look for latest driver Download - SAVE - go to right click on
and RUN AS ADMIN (This is your fallback.) REBOOT after each driver installation.
NOTE : Sound drivers often rollback so check the version after installation and thereboot to see if the version you installed is there, if not repeat the install - rebootuntil it is. It can take several tries depending on how many rollbacks it does.
Then do same for Device Maker's site.
Manually look at manufacturer's sites for drivers - and Device Maker's sites.
http://pcsupport.about.com/od/driverssupport/ht/driverdlmfgr.htm
Installing and updating drivers in Windows 7 (updating drivers manually using the methods above
is preferred to ensure the latest drivers from System maker and Device makers are found)
http://www.sevenforums.com/tutorials/43216-installing-updating-drivers-7-a.html
Error “the Audio Service Is Not Running” When Opening the Volume Mixer in Vista
Also Right Click Speaker near clock - Playback Devices - right click in the box area -check Show disable and disconnected devices. Highlight speaker and on the lowerRight click Properties check settings for Device Usage enabled and so on. Also dosame for Configure on Lower Left of that box.
In Control Panel you can also look for an Audio Manager along with the Sound Settings.
Open the Playing Audio troubleshooter
http://windows.microsoft.com/en-us/windows7/Open-the-Playing-Audio-troubleshooter
Problems with sound and audio or no sound - a Mr Fixit
http://support.microsoft.com/gp/no\_sound
No sound in Windows
http://windows.microsoft.com/en-us/windows/help/no-sound-in-windows
Tips for fixing common sound problems
http://windows.microsoft.com/en-us/windows7/Tips-for-fixing-common-sound-problems
Speakers and other audio output devices
http://windowshelp.microsoft.com/Windows/en-US/Help/a43f3a31-6d9f-49d1-be22-e2f47b8b1f2c1033.mspx
How to Enable Hidden Audio Devices in Vista
http://www.vistax64.com/tutorials/143447-audio-device-enable-hidden-devices.html
How to troubleshoot sound problems that you experience after you install a Windows Vista
Service Pack
http://support.microsoft.com/kb/948481
Hope this helps.