I would go for a Intel mother board with Core 2 duo possessor. if you game a little, i would go for 1gb.. as a minimum, but 2 gb is not bad either remember to buy DDR2 ram=)
HD you should go for a SATA2 disk, it is quicker that the old IDE disk, and could transfer up to 3gb/s
Graphic card: it is 2 base models Nvidia and ATI. in gaming I would go for Nvidia, ati is not bad, but, have had ATI for a long time, and have now changed to NVidia and is happy with that.
as a good all around card, that you could play all the games on max I would go for Nvidia 9700 series. happy hunting for a new computer