I have a printer hooked up to a computer running Windows XP. It prints fine from that computer, but I'd like to set up other computers (running Vista and 7) to print from it as well. I tried setting up printer sharing, but it wouldn't work because the client computers needed to install the print driver as well. (The driver itself has been discontinued and there's no version for Vista or 7.)

Is there some (hopefully free) software I can install to, say, add a virtual printer that sends the data to a host computer to print it, rather then having to directly access the printer over the network via the Windows printer sharing model?