Home built system (any ideas?)

thanks for clicking here and read..

ok first off im trying to get a computer that can run alot of the latest games going to b out, but i also like something able to handle fallout 3 falllout NV with out all the crashing if it can b helped (playing on my laptop..)

i like to build something under 600-900 bucks US cash (unless i can get something cheaper and i would like to stay with AMD type GPUs (they seem to cause less trouble)

im have a few ideas.

i5 intel
8gigs of ram
500 or more HD space
DVD type drive and if i can a solo pure DVD drive (i had cases where my dvd drive would scratch my dvd in a surter place making it unreadabul... i think its because its a DVD burn..)
i have a case i like already picked out its 79 bucks and it looks cool (but im up to make my own case threw parts also so it has my soul mater of speeking in it.. xD)
i have a few mother boards i like but there really pricy... (i guess its something i can always update later..)

but if u can i like to have a way to add the OS in this price if u can.

things came up and i cant get my 1000 buck comp i wantted last year.. >_> so this will do...