I recently put together a Mini-ITX NES PC, I know this has been done before, but I thought I'd post a couple links for people to check out 
Mini write-up: http://not.hellalame.com/nes/
Picture Gallery: http://not.hellalame.com/nes/gallery.html
Quick System Specs:
[*] 1.1a Celeron
[*] Freetech P6F135 815 MoBo
[*]256MB RAM
[*]30GB Hitachi HD
[*]24x Slimline CD-ROM
[*]125 Watt 1U Power Supply
I also bought a PCI Video card (GF440mx w/64MB) with TV-Out I will be adding soon, and will most likely be making this a HTPC!
Mini write-up: http://not.hellalame.com/nes/
Picture Gallery: http://not.hellalame.com/nes/gallery.html
Quick System Specs:
[*] 1.1a Celeron
[*] Freetech P6F135 815 MoBo
[*]256MB RAM
[*]30GB Hitachi HD
[*]24x Slimline CD-ROM
[*]125 Watt 1U Power Supply
I also bought a PCI Video card (GF440mx w/64MB) with TV-Out I will be adding soon, and will most likely be making this a HTPC!