feedback through external components

[stevebm29]

I'm running an HP dv6000 laptop w/vista home,I use the computer for a lot of media,I have it hooked through the 3.5 sound jack and also s-video jack.My problem is that I get feedback on surround sound and i can see it on TV screen.When I unplug laptop from AC and it runs off battery everything is fine.I bought an AC filter thinking that it would filter  AC power/feedback but that hasn't worked either.HP tech.support no help either.One of my friends has a newer HP dv..... and it has a filter looking thing on the AC cord I've tried that also,no luck........any ideas?

[Geek-9pm]

Without more detail is is hard to make a recommendation. Are we to assume that you do not mean acoustical feedback?
Is this an external sound system other that the one recommend by HP? If so, don't expect HP to troubleshoot other people's products.What kind  of external sound system is it?

Real good EMI filter costs more than an average sound system.

http://www.computerhope.com/jargon/e/emi.htm

[stevebm29]

I have it plugged in to a Pioneer HTV-C1 surround sound system and everything is plugged in thru an ESP digital power filter.Any help?