and again what does your bike have to do with what he asked about??
multi speed freewheel to singlespeed conversion.. ... already been done MANY times nothing new here!!
http://sheldonbrown.com/singlespeed.html
Conventional Freewheel-type Hubs
The cheapest way to convert a multi-speed bicycle into a singlespeed is to use the original rear hub, assuming that it is made for a conventional threaded freewheel. A single BMX freewheel will thread right on. Unfortunately, the chainline is likely to only work with your granny gear unless you re-space the rear axle and re-dish the wheel.
Cassette Hubs
It is easy to convert a Shimano cassette Freehub ® for singlespeed use. The simplest way is just to remove the derailers, shorten the chain and thread it onto the chainwheel and rear sprocket of your choice. This is less than ideal, however, because you've got the extra weight of the unused sprockets to deal with, and the chainline will probably be crooked. The sprockets used on multi-speed cassettes are designed for easy shifting, which is not a good thing on a bike that isn't supposed to shift!
The better way to convert a cassette Freehub ® is to remove the 7-, 8- or 9-speed cassette and replace it with a single sprocket. You will also need a bunch of spacer washers to hold the single sprocket in place. You can often get a suitable number of spacers by taking apart a couple of discarded, worn-out cassettes.
Having a single sprocket sandwiched in a stack of spacers makes it easy to get the sprocket properly aligned for perfect chainline with whichever chainwheel you choose to use in front.
You can use one of the old sprockets from your taken-apart cassette, but it you are less likely to have accidental derailment if you use sprockets made for single-gear use. The best choice for this is to use BMX cassette sprockets. These sprockets are quite inexpensive, and are available in a range of sizes. They have taller teeth than sprockets designed for derailer use.
http://www.pinkbike.com/forum/listcomments/?threadid=144750
http://www.instructables.com/id/Single-Speed-on-the-Cheap/
http://forums.mtbr.com/singlespeed/homemade-ss-freewheels-step-step-photo-guide-373319.html
http://www.youtube.com/watch?v=KOOxSaDDV5I
http://singlespeedcomponents.co.uk/advice.html