Network Connection Completely Disappeared?

I had a network connection to the main family computer that just completely disappeared after I got back on it. It had been on all day because it was defragmenting, but a few minutes after I got back on it (I had just sat down in the chair and sent a couple messages on a chat I was in and dismissed an "Oh, Windows Media player found another WMP on main computer! Wooo!" notification) and then it was gone.

I assumed the internet had crashed so I gave it a couple hours, no internet. I stayed up longer waiting, writing, playing some games, but nothing. I didn't check the Network computers thing until now.

Usually even when the internet crashes the main computer still shows up in the computer list but it was just mine then. It seems like it totally dropped the connection and it can't find it again when I try to create a new one. It's not like I watch p~rn or download anything I'm not supposed to download so...

And the network icon doesn't have a big red no connection at all x - It's just the two computers, no world icon, no x. I've tried booting in safe mode with networking, nothing, 'netsh winsock reset catalog' + 'netsh int ip reset.log, nothing, create new connection, nothing, and repair memory problems, nothing. : Microsoft Security Essentials found no viruses after a full scan, and it had been updated hours before the internet had a tantrum. I recently uninstalled Malwarebytes because according to a friend its update crashed her computer so I have no other virus scanner to use.

Oh, I'm runnning a Windows Vista Home Premium. Mine is genuine, it came with the computer, but my father had the bright idea to use -my- Vista disc to install it on the main PC, so it's all 'rawr not genuine' though as far as I know, my father's W7 laptop is still running just dandy.

We use a D'Link router, and it's worked fine until now. I don't actually know how my computer is connected, I'm pretty sure it's hardwired to the modem or router, but my father's is wireless. I've been searching like mad for the router's wireless USB thing, but it seems to have walked out the door.