Help:I want my old HP printer to be compatible w/my new Dell computer. A parallel to USB cable doesn't work.

My old Hewlett Packard PSC 500 printer has a parallel port and is not compatible with my new Demension E310 Dell computer. What can I do to be able to use my HP printer (which works great) with my new computer. I already tried a parallel to USB cable, but the parallel end does not fit into my printer. Any ideas? Thank you.