Power Supply?

For most of these general questions you should do a google search for the answers. In general, PSU requirements depend upon the video card you're putting in and whether it is one that draws a great deal of current. eg. 8800 nvidia card you will need at least 550W PSU. Also, if you do add a greater load and say 2-3 extra hard drives and you do overclocking, then a bigger PSU will be better as there is more likelihood of a strain on the PSU. So always have extra capacity to handle additional power supply requirements. A general 450 PSU will handle most home system requirements unless you're adding a fast graphics card and multiple harddrives and fans.

The mother board spec calls for the type of power supply you need. In general, out put power (watts, 20W, 30 W, etc) and the connection types of the output cables that plug into the mother board, CD ROM, hard drive, etc,