What is the maximum length of D+ and D- cable that can be run. I want to extened my wireless modem. The Modem will have a 5 Volt supply right next to it and I want to run the D+ and D- back to the computer. Do I need to put a booster in line andif so please can you point mein the direction ofa circuit diagram

 

3-5 meters depending on the speed.
There are devices to allow USB cables to be extended via CAT 5 cabling (up to like 300 ft) or even Fiber (up to like 1600ft)