Firstly a few questions ...
- system fails to detect IDE on startup or will not auto detect in BIOS setup?
- are the printer port settings in BIOS setup according to the printer manufacturers specifications?
- is it the proper parallel cable for the printer?
Secondly a long distance diag ...
The IDE and parallel port can interfere with each other in DMA features and settings. Of course, knocking some cable loose can have that effect to. !Hot-Plugging-In a bi-directional printer can frymotherboard circuits, (especially if it comes out of the plastic wrap and gets hooked up right away), but since you powered down first, that's not it! Could be the power supply has hit the max and will not put out that few extra watts at boot time ???
Insure that all connectors are tight and as required, (drives jumpered, I/O ribbons oriented properly, power plugs, etc);
Check that there is only one parallel port I/O device installed, (or move one to IRQ7 at 378h and second to IRQ5 at 3BCh);
Look carefully at the BIOS settings, especially DMA and IRQ assignments.
Please post a comment if you need more info or want to provide more for us ...
Good hunting, I hope this helps you get it running again soonest.