The Celeron will move to all current 775 socket boards.
You'll have to do a repair install or reformat when you change the board to renew the Hal Config.
Good news is you can D/L Windows 7 RC1 grom MS and use it until next year then upgrade to the retail.
The power supply depends mainly on the CPU MB and video card used.
Have a look over these>
Link Disc. Cost Rebate
http://www.newegg.com/Product/Produc...82E16814130468 GTS250 $124.99 $15.00
http://www.newegg.com/Product/Produc...82E16813128372 UD3L $94.99
http://www.newegg.com/Product/Produc...82E16820231209 DDR2 800 $54.99
http://www.newegg.com/Product/Produc...82E16811119068 Case $44.99
http://www.newegg.com/Product/Produc...82E16817139005 650TX $99.00 $20.00
$418.96 $35.00
$383.96