First run Windows Update to see if any drivers
are cued in optional Updates. After updating all drivers, for any missing in Device Manager go to the Dell Support Downlloads webpage for your tag number and install the Sound driver
to see if that helps.
I would not change out any drivers provided by installer or optional Updates unless there are performance problems, however, as unlike XP Windows 7 is the authority on its own drivers.
If that fails try restoring the hotlink to Recovery Partition to your F8 Repair My Computer menu, as long as you didn't delete the Recovery Partition during clean reinstall. If you did or it won't restore link and then run, try marking the Recovery Partition Active, then reboot to see if it will autostart: Partition - Mark as Active
. Note that you may need to use Option Two using Diskpart from the Windows 7 Installation DVD Repair console Command Line to mark Windows 7 Active again
If not you'll need to order Recovery Disks for your tag from Dell if you didn't make them at computer setup, or post back for any more help on problems with your clean install - which is a superior install anyway: Reinstalling Windows 7 Dell Recovery Partition - restoring F8 link Dell Restoring Your Computer´s Software to the Factory Settings