I have an 8800GT and I was wondering if its possible to hook a console (specifically a Nintendo 64) up to my computer and get the console's video output to show in a window or something. Is that possible?

why would you want to do that. rofl

use the emulator Project64 and you can run the games on your pc (in a window or full screen) and often with AA and AF for much better image quality than before. need the roms of games or some device to read from cartridge into pc (im sure its ok  to download roms of games you actually own for this purpose).
 
http://www.pj64-emu.com/

 
There are places to find these downloads, though some of the games (specifically Nintendo developed games) can be hard to find.
 
One place to look is ...
 

"There are places to find these downloads, though some of the games (specifically Nintendo developed games) can be hard to find.  
 
One place to look is ..."
 
Try torrents, I had to wait 3 days, but I got 335 of the most popular roms for PJ64

An emulator is great and all...but its not the same. I want to use the N64 controller. How can I hook my N64 up to my computer? Does the 8800GT support S-video IN?..I have an adapter that came with my card (it plugs into the S-video port) that looks like it will accept the 3 connectors from the N64.
 
Edit: http://www.gigabyte.com.tw/Product [...] uctID=2720
Looks like it doesn't support input?

 
There might be an adaptor somewhere on the internet. However if you cannot find one you can just buy an xbox 360 wired controller and connect it via usb.

http://www.ztnetstore.com/product_ [...] 74957d5cab
 
Something like that would work.  Can't speak to the quality of the site or the adaptor, but it was the first one that came up with google.

 
 
I sure hope you own all 335 of those games on original N64 cartridge.    
 

right so he would have spent maybe $1675 on cartdiges asssuming they were at $5 a peice and bought themm all when they were this cheap? lol  

He best not ever upset me or I'll be email Mr. Nintendoshi Kong Country with a tip off.  
 
Off for a Wii

A DVBT TV card is what you need :- http://www.yoyotech.co.uk/product_ [...] 01fb6ba8bf

So can I just get a decent cheap TV tuner?
http://www.newegg.com/Product/Prod [...] 6815116024
http://www.newegg.com/Product/Prod [...] 6814122180

The  Hauppauge one should work as it has composite input and audio input.

This one has the inputs I want, should I get it?
http://www.newegg.com/product/prod [...] 6815116633

Be warned: the delay on these cards is heavy, many consider it too heavy to use for console gaming (myself included).  The quality is also low, unless it uses hardware instead of software  to process the video, but if you let the hardware do it, you get even more delay.  See the tv-card section for more detailed information.

Yes I did own every cartridge, I can also balance a TV on my forehead while climbing a ladder in a windstorm.
 
You would be amazed.