I have a usb web cab which I would like to place about 6 meters from my computer so that I can use it as surveillance cam.
I cut the usb web cab's cord from middle and attached a cctv (5 wire) cable but on connecting with the computer, the computer says "unrecognized device".
Which kind of wire should I use?

There are a number of products available. Check here: CablesDirect - USB Extenders and Active Repeaters, USB Cat5 Extenders (http://www.cablesdirect.com/search_usbext.asp)

There are power and data cables on USB. The capacitance of the cable kills the speed and distance without drivers and receivers.
The 16' extender should be plenty. I've used two of these together before.