The laptop and the PC are at about the same distance. In fact, I've currently got it hooked up so that my PC is wired to my laptop and using the laptop's internet connection. Dodgy and doesn't fix the base issue, but it works for now. This also answers a few things:

1: Wired connections work fine
2: The router is having no trouble transmitting the data far enough.

Honestly, the thing bugging me most about this is how bizarre it seems. I know a fair bit about how computers work, been using them since I was an early teenager, and nothing about this problem seems to make any sense. The only thing that comes to mind is that my PC may be having issues using it's own hardware. I've noticed intermittent issues with my USB mouse and keyboard, and with a USB headset (Regular audio ports work fine though), so there's the possibility that something's faulty with my USB slots that's causing anything plugged in to underperform, AND my NIC card is also faulty.