I'm in the same boat. I have an HP LaserJet 5MP that I had connected to my old Windows XP computer with a parallel to usb cable. Worked great for 7 years (yes I had my old computer that long), but old PC finally died and I set up my new Windows 7 computer but can't print.
The printer installs automatically when I plug in the usb cable. I also tried adding the printer manually and the driver does appear in the list of printers (using Windows update feature). It says it was successfully installed and when I run printer diagnostics it says it's working. But anything I try to print, including test page, gets stuck in print queue. If I restart computer, everything in queue prints as soon as Windows starts to load. Which tells me perhaps something in Win 7 is blocking the printer from working? If it worked once, then it does work!
Maybe Windows 7 does not support the parallel to usb cable?
I found this page on the HP website: "HP LaserJet - Products not supported in Windows 7". The printers that HP shows are no longer supported in Win 7 that are similar to the 5MP, are LaserJet 5L Extra, LaserJet 5se, and LaserJet 6L Pro. But no mention of 5MP. I love this printer, has been great all these years, never broke down, uses very little toner and the toner is super cheap. I really don't want to get a new printer. Any help would be appreciated!