Windows 7: headphones don't work on Windows 7 only drive

I have one hard drive that I multi-boot with XP and 7. Headphones work fine. Other hard drive is just Windows 7 and headphones don't work (speakers work fine). I have tried unplugging and plugging them in: search for new hardware and rebooting many times, all with no luck.
When I go into "sound" in control panel and unplug my speakers it tells me that there is no audio device attached (this doesn't happen on my dual boot drive) and when I try to add a new device, it searches endlessly for new devices and not only never stops, but never finds any devices.
Don't know if it matters since all of my hardware works when I use the dual boot drive, but I have a Dell XPS 720 aand an X-fi PCI sound card although the headphones plug into the front panel of the computer, not the sound card (yes I tried plugging directly into the sound card)
Thank you for your help.