Buying a wireless router will work, all you do is get the two computers on the same domain/ workgroup and run the file sharing wizzard to help sort settings out. Then create a share folder on each PC, you'll then be able to share files between to two.
Once you are networked together you often just have to drag and drop the files to the new positions.
http://support.microsoft.com/default...b;en-us;304040
http://www.practicallynetworked.com/...ilesharing.htm
http://www.theeldergeek.com/quick_gu...le_sharing.htm