umm,
1 tb hard drive
at least start with 2 gb if not 4gb memory
amd quad core or intel i3 or i5(which everone is better)or even intel core 2 duo or quad
i'll get windows 7 my self.
Well based off your 300 dollar budget that ain't gonna happen.
A terabyte drive will be about 50-80 bucks.
4GB DDR3 will be about 100 bucks.
AMD Quad Core will be about 200 dollars.
That will exceed your budget and you didn't even bother listing other important stuff like motherboard, video card, etc.