What you're describing is certainly possible as part of my system is setup that way.
I hard wired my home for sound and video years ago, long before I got into computer technology, so I had to adapt what I already had to the newer technology.
My media computer is in my workshop and I wanted to be able to control it from my bedroom, about 35 feet away.
I first hooked up A/V cables to the sound and video cards and to the existing cables to my bedroom (and the inputs of a VCR).
In addition, I got 2-15foot USB extention cables for a total of 30feet to hook up my 'Gyration' mouse & keyboard (RF but only a 25' range - they now have one with 100' range) and voila, I could control, watch and listen to my computer!
However, while watchiing streaming video/photos etc was fine, readabillity of text sucked. So I got some VGA monitor extention cables and put a monitor in my bedroom as well. I can now run MC (or anything else) and view the app. on the monitor and with MC's display configuration ability when I want to view full screen, MC will send the image/video to the TV.
I don't know how far you can extend the feed for the monitor, mine is 45' without any appreciable degradation. When running any line level or video feed keep it at least a foot away from any parallel AC lines and cross AC lines at right angles if must.
Instead of running A/V cables you can use A/V transmitter/recievers like the ones Radio Shack sells for about 70$.
There are other options today, Mastiff is really the expert in this area around here, check out his website:
http://mastiff.now.nu/