Front headphone jack and front speakers not working 5.1

I have a Dell Dimension 9150 Windows XP Media edition sp 2 and Im having speaker/headphone jack issues.

I recently installed a memory upgrade and my speakers were working properly prior to that. I spent the last two hours on the phone to Dell Support hooking and unhooking speakers, checking to make sure everything was on and not muted, running diagnostics etc stc and they said couldnt help me....

The problem is that i am not getting any sound out of my front right and left speakers, nor is my front headphone jack working (the USB ports work fine). Dell said that my front speakers were faulty, but after playing around a bit myself (plugging in headphones which dont work) i got the speakers working but lost my center speaker and my rear right speaker *pulls hair* I reset defaults and im back to two front ones not working. Anyone have a clue here? I've upgraded the driver, they said it wasnt my sound card...i just dont want to go and waste money on a new speaker/sub system if im going to have the same problem.

Also I teasted the front speakers with my discman and they both worked fine when connected to that. 

Help?! Please?

****I ended up calling Dell back and asking about the memory overkill thing and the tech i talked to this time tried one thing that the previous tech didnt....he turned off my internal sound in BIOS.....and it worked!

problem fixed!