Memory is very cheap now. Two 1G dual channels can be used. If you want to upgrade in the future, you can consider installing only one 2G. Anyway, the use of dual channels is not obvious.
4. The graphics card 9500GT is the mainstream at present, but the price of 599 yuan can also buy the second-line brand 9600GT, even the colorful 9600GT is not much 100 yuan. If you pursue the quality of the game, it is better to buy 9600GT directly, so as to avoid the pain of not playing the latest game in the future.
I don't know what kind of chassis you are using. The original chassis power supply will definitely not work. Now the power supply is 24P. You should buy a new power supply, recommend Hangjia or Great Wall, with a power of at least 300W W W. In addition, some old cases are not very good at heat dissipation, and now the CPU and motherboard are very hot. You'd better install a chassis fan to help dissipate heat. I see that almost all your computers have been changed, and I don't care about the money. If I just buy a new chassis, forget it.
6. If you want to keep the old hard disk and optical drive, you should pay attention to the support of IDE interface when choosing the motherboard. It is best to find a motherboard with two IDE interfaces. However, most new motherboards only keep one IDE interface, so you can only use two-in-one data cable to connect, which will affect the stability of the system.