A customer calls saying that he installed a new printer, and now his dial-up modem has stopped working.

It sound unusual, as printers and modems shouldn’t interfere with each other.

When I get there, hitting the dialup shortcut give a error 797.

Since the modem doesn’t even show up in device manager and detect new hardware devices also doesn’t find anything, I decide to open up the PC and take a look.

The modem card seems to be plugged in correctly, but when I go to pull it out, it seems to slide out very easily… I plug it in again, and I notice it doesn’t fit well.

The metal backplate will only fit by pulling it slightly. When screwing in the backplate, the card is pulled slightly (in a lever fashion), such that the pci pins furthest away from the backplate are pulled out of the pci socket (but only slightly).

I’d say the card wasn’t fitting flat/squarely into the pci socket, so a bump to the case (by moving the PC to insert the printer USB cable) dislodged the modem card enough for it to lose contact.

To fix: a slight bend in the PCI backplate was all it took.