No Major Mistakes, but things could go better.
PSU seems, ok, better buy Branded PSU for stable operation, or check, on motherboard that your +5v rail is stable.
H/D: dont buy Maxtor, they are cheap, but eventually in a years time, they start making Noice (Loud noice out of spindle), get Samsung, Hitachi or at high end, get Seagate, WD.
memory looks OK, beter check out with your Mobo's Manufacturer's QVL. although I have seen no issue people using Geil.
motherboard = better wait for nForce5 chipset board. they might be expensive, but nForce5 has better technology that even Intel didnt introduced in their latest chipsets. though manufacturer is good, but I've seen MSI's boards performing better on nVidia chipsets.
CPU= spend some more money (dont buy fance lights, etc) and get CPU on Toledo core 4400+ (with 2 X 1MB cache)
DVD= LG may not be a good choice, see if you can find Plextor (they are most expensive, but best), else Pioneer (very good), and Sony as well.
Graphiccs card = very good choice to get nVidia, but, see if you can find eVGA's manufactured. they give life time warranty on thei cards.
Intel Core2Quad 2.66Ghz 12MB L2-Cache
4096MB DDR Kingston Hyper-X
XFX 9600GT AlphaDog
Seagate 2 X 320GB SATA2
LG L246WH Flatron 24"