Dell XPS 400 Sub Woofer/Center Chanel/Satalite Speaker issues

Hello,

     I have a Dell Xps 400.  I recently had it crash, and I replaced the hard drives, and opperating system.  I Plug it in and everything works great.....but no sound.  I run through all of the windows troubleshooting, and nothing.  I finally went through the device config, and went through the sound tests.  When I plug my headphones into the back where the 3 inputs from the sub go, I get the sounds, faint, but they are there.  Plug the subs back in and nothing.  I pulled out some old computer speakers,  ( just two speakers ) and nothing.  I put it back in my desk, and plug my headphones into the front headphone jack, and no sound again.  Has anyone run into this before?  Any help would be appreciated, thank you!

Kelly