HPT45xi and Imac--help me make them talk to each other!

I recently joined the Mac world after being on a PC for years. I have an IMAC, OSX 10.6.6. I also have an old HPT45xi all in one printer. The ink usage on this printer is great so it is really cheap to run--that is why I do not want a new printer. But I can't get the IMAC and the printer to talk to each other. The printer is connected to the IMAC through a parallel port USB connector. The IMac recognizes the printer and I have been able to install the settings for the printer. When I send a job to the printer, it powers up, pulls in paper and makes the "i'm gettng ready to print noise" and then it stops with an error message to "reconnect to the PC". Then it prints one line of garbage. I have spent hours trying to get this to work and am completely frustrated. Are there any suggestions on how to get these two to talk to each other nicely? Thank you.