Shade-tree mechanic blinded by sun

Apparently I've been neglecting my hardware duties for too long: last night I opened up the Old Box and stuffed into it a fresh new PCI card with four USB 2.0 connections thereupon, and I was so unbelievably clumsy I'm surprised I didn't drop-kick the tower into the corner. In fact, the machine wouldn't boot until I opened it back up and manhandled the card into a different slot; unless there was some vague grounding issue that I overlooked, I have no idea why.

And while it's probably a losing battle to keep a Windows 98 (albeit Second Edition) box going after all these years, it's either that or buy a new scanner.