Print commands not transmitting to printer

I am running XP Professional SP2 with auto updates from Microsoft on a Dell
Inspiron 8500. The printer is a HP Laserjet 4 attached via LPT1 port.

The print command operates correctly but does not reach the printer.

I have checked the printer and cable and these work correctly on another
computer.

Troubleshooting through windows says everything is correct.

Every check says that the printer and port are correctly configured and
working correctly.

Online diagnostics from Dell confirms this result.

I have attached an old Epson dot matrix through LPT1 with the same result.
On startup, the printer is recognised but the print command does not reach
the printer.

I am left with the conclusion that something has happened in Windows.

? ? ? ?