I'm running Windows 7 x64 and I have no issues with sound or video.
As mentioned already, make sure you have the correct and updated audio drivers.
Some manufacturers don't list 64bit drivers separately but instead include them with the 32bit drivers.
For example, my MSI laptop came with Windows 7 Home Premium. They do not advertise that 64bit OS's will run on the system however the hardware fully supports 64bit. When I installed Windows 7 x64 I realized that they did not "offer" 64bit drivers however after extracting the "32bit" version of the drivers I realized that every one of them included the x64 .cabs, .dlls ..etc.
So, the point of that is...just make sure your using the correct driver. If your running x64 make sure the drivers are x64 (or included as mine are) as well.
Dell actually does list there 64bit drivers separately from a drop down menu.
http://ftp.us.dell.com/audio/R171788.exe
should be the one you need. Also with Dell laptops, if you have reinstalled the OS you need to be sure that the drivers were installed in the correct order.
Notebook system software HAS to be installed first and is located under "system Utilities", then Chipset, ect. Here is the install order for ALL Dell systems.
http://support.dell.com/support/topi...=dhs&~lt=print
I used to work for Dell in tech support and can contest the NUMEROUS problems and complaints that arise from improper driver installations.