HDMI to DVI-D connection problem...please help

High I'm new on this community..i'm reading much of the forums here that might help with my problem but its seems i'm out of luck thus i have a different scenario though, i think.

i got a pc 23" acer monitor that has vga and a dvi-d dual link input with hdcp capability. i got a xbox360 that works perfectly by connecting from my xbox hdmi to my pc dvi input, im using a hdmi cable and a dvi adapter in my case. now heres my problem:

i got a set top box which has a rca and a s-video output, since i know that a straight forward connection by using a simple cable from my set top box to my pc monitor wont work...so what i did is i bought a converter from ebay that could convert a signal from rca/ s-video to hdmi only so when i try to connect my set up box rca output to my video converter rca input and from my converter hdmi output to my pc monitor dvi input using the same cable as what i mentioned above and then i dont get a video diplayed on my pc monitor. i checked all of the connection the power of all sources, everything is just in place and powered on. i tried using the s-video connection as well still no picture.

my converter is not broken thus when i try my set top box(rca/ s-video-output)--->{(rca-input)converter(hdmi-output)}---->(input-hdmi)HDTV and it works, so this confuses me.

set top box--->converter(HDMI)--->(HDMI) HDTV === WORKS!!

set top box--->converter(HDMI)--->(DVI)PC monitor === Doesnt WORK!!

is someone there who knows what's wrong?
please i need your suggestions and bright ideas to help me out.

Thanks in advance.