How to Share 3G EVO/NITRO without a router 2nd Method:
Probably you don't want to buy a wireless adapter because you have a built-in wireless card installed on your laptop and you're planning to share your evo/nitro connection through your built-in wireless card.
1: You should be running Windows 7 or 8 on your machine (Newer Linux Systems are also capable of doing that.) with all the important updates installed.
2: Your wireless adapter must support AP (Access Point) functionality. (Any wireless adapter that has a specific driver for win 7 is supposed to work).
P.S: One thing to be noted here is that you can share your connection using this technique from your extrenal wireless card/usb as well provided the two conditions are fulfilled.