What will you be doing with the PC? If you are just browsing the internet (which I hope is the case with a Celeron 2Ghz) you don't really need anything other than something to connect a monitor too. You could really just get whatever is the least expensive.
Is four year old ATI Radeon HD 3850 too good for this system?
I don't know what you mean by "too good." It is certainly better than the rest of the components in your system, so I wouldn't spend more to get it, but if you have one already, laying around, it wouldn't hurt to use it
Just one more question, to be sure:
And if I'd like to use ATI Radeon HD 3850, would the PSU fit for that?
Do I need some complicated power connections to the PSU with wires and connectors I don't have and (I'm not sure there are 4 or 6 pin power connectors on the motherboard, there is just something like this http://www.motherboards.org/images/articles/guides/P4_c... that comes from PSU)?
(Im just asking this because I can get Radeon HD 3850 cheaper than Geforce 6200 and the other cards I mentioned.)
@ musaire - the 3850 require a 450W PSU with 25A on the 12V rails. You have only 16A. Windows 7 require •DirectX 9 graphics device with WDDM 1.0 or higher driver. Check that the 6200 is DirectX 9 capable.