I take it some of this stuff is left over from last build? The issues I have are as follows.
The CPU is ok, but if you are planning on overclocking it the motherboard will probably hold you back some. The G31s aren't known for their overclocking ability.
PSU: Xion? Really? Unless you are reusing this, switch to a better brand. Heck, if you are reusing this, switch to a better brand. You don't want this to blow up and take out your stuff.
GPU: Another thing I get the feeling you are reusing. The G31 already has onboard video, whats with the 7900GT? You also don't need this card, as you aren't doing anything graphically demanding. If you are buying this, see about getting a more modern GPU, a 43xx card from AMD would be great.
HDD: An old 80GB 2MB cache harddrive? Let me guess, another thing you are reusing? Graphics editing loves ram, which you have, and fast harddrives, which you don't. You don't need a new 1TB drive, but I would look into getting a modern 250-500GB drive.
I'm assuming at this point your trying to upgrade on the cheap. While the mobo, cpu and ram are a good starting point, you still have some issues. Let me/us know if my assumptions are correct about reusing.