when you rebuild, try putting the add-on cards (sound card, net card, etc) in different slots than they were in previously. This will force new interrupts and memory allocations to be used, which might clear up some things. If you have a manual for the MB, it should show which slots use which interrupts by default. Some bioses allow you to change this after the cards are installed, as well.
good luck.
oh, and check Dell's website for your particular model to see if there are any known issues and/or fixes for any of the included hardware.
