Just to make sure I have understand what you need.
PC has 6850 card with HDMI/DVI
TV has Component(3 RCA cables + Audio)
If so read on....
I would watch out for the cable adapter options as you need to have a card that can pass analog over HDMI, I do not think the 6XXX cards do that.
kelvin08113 is on the path, You need an active(powered) adapter to convert the digital signal from HDMI to the analog Component(3 RCA) + L-Audio + R-Audio.
The problem is that the linked adapter goes backwards. Component to HDMI
Something like this
HDMI In to Component + Audio out, BUT i have never used this adapter and can not comment on its quality.http://www.newegg.com/Product/Product.aspx?Item=N82E16812705073