maui7

I just purchased an Alienware system with the 5.1 promedia's. The day it arrived I took the system over to a friends house and hooked it up, sounded great, did some LAN gaming. Brought it home, set it up and got nothing but base sounds and some hizzing/crackling from the speakers. Called tech support. Stepped through every thing they could think of and sent them back for replacements. Ok, new set arrives, quickly hook them up - sound great! Unplug them and get them in to the postions I want them in my computer room and bingo! Only the sub sounds can be heard. If I turn it up enough (almost max volume) I get the same loud hizzing/crackling from all off the speakers (except the sub) that I had on the first set. I tried every button I could find on my Creative sound card (Live 5.1) to see if I had my volume muted and everything seems fine. I can plug in my old Altec Lansing and they play fine off the sound card - course they are only a 3 speaker set up. I am doubting I have have two bad sets of speakers, and I am thinking I must have done something wrong in the setup or with my sound card - but for the life of me I have no idea what. I am extremely frustrated at this point as I have unhooked and rehooked up these speakers so many times now. Any help would be appreciated!