Well, the two best ways of connecting the printer is either
a) connected the way you have it at the moment via LPT and USB
b) connecting the printer to the network
It is possible to connect the printer to just one PC and share it. It is not very reliable, and that PC will need to be switched on and in Windows for the other PC to print. The instructions for which can be found here:
Share Your Printer Over a Home Network Using Windows XP