EDIT: Your Best Fiend is correct I misread the question. My unqualified YES was to mean that you CAN do this change, not that it would be difficult. AndrewWs suggestion is the best way to get started, I hadn't seen the performance bike kit before.
An unqualified YES!!
Ignore the first two answers, this is stupid simple. I've converted two road bikes with vertical dropouts using a chain tensioner that mounts to the derailleur hanger like this one:
The other thing you'll need is a rear wheel with a threaded hub instead of a cassette, a track cog and lock ring if you want a fixed gear, or a single speed freewheel. All of these parts are readily available.
If you go with a track cog for a fixed gear, you'll need a track chain since the pitch is different.
You'll also need to be concious of the chainline. The chainring and cog should be pretty much lined up or you'll risk the chain hopping off - especially at high cadences. Pick the chainring you're interested in, and mount it on the inside of the crank arm. When you 'sight' down the chainring from the front of the bike, the rear cog should be right behind it or damn close. If you lucky enough to have a bottom braket with adjustable cups, you can offset it slightly to compensate. Otherwise you'll need to look into a different bottom bracket spindle. Be carefull with this part, if you shift it too far inward, you may end up with the chainring rubbing against the chainstay. You might be able to compensate for this by a smaller chainring/cog combination to keep your gear ratio.
Still, the easiest way to do this is to start from scratch, build up a bike from used parts on ebay (using a frame with horizontal dropouts), Half the joy of doing this is actually _doing_ the work. You end up with a finished product that you can show up on rides and say "I built it myself". Not only _can_ you make this conversion, I think you _should_ make this conversion.
Or, you could just go out and buy the bowery, but that's no fun!