High pitched noise from speakers

[steve noob]

My speakers give off a high pitched, whiny noise now that I've moved my computer to the other side of the room and made a 35 ft extension of cables going around from PC to my desk. Sounds like fan/hard drive noise.

I am using a 1/8" stereo extension cable connected to my onboard sound. I have tried USB sound card with no luck because the analog interference travels through the USB extension cable and hub!

There is only slightly less noise when separating the audio cable from the others.

This probably means I need well shielded cables - any recommendation?. Would an internal sound card make an improvement, and which would I try? Would a different power supply help?

 

[steve noob]

I'm thinking of trying this cable: http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021815&p_id=5603&seq=1&format=1#largeimage

 

[ur6beersaway]

Maybe one of these on the power cord:http://www.amazon.com/s?ie=UTF8&keywords=ferrite%20beads&page=1&rh=i%3Aaps%2Ck%3Aferrite%20beads