everything you say is still pretty vague. what are the specs of your old laptop? what kind of games do you plan on playing? if you're not gonna do any video editing or any other applications that use a lot of memory and CPU, then you really don't need to spend that much on a comp. for surfing the web and typing documents, pretty much any computer can do that. even a $100 budget comp lol
you can get a low end dual core CPU. i would probably recommend AMD since they are more bang for the bucks for common tasks. intel i'll admit has some better high end CPUs but you don't need all that jazz. well... it's a lot more technical than that and i'm just generalizing, but you probably should go with AMD
for other parts, do you really need 2GB of memory and 500GB HD? well for memory, ddr2 is almost free so might as well get 2gig. but for the HD, 500gig is a tremendous amount for regular tasks. 80 or 160 gig should be plenty. if you ever run out, you can always get an external (or another internal and set up as slave) later, as it will cost even less. but for now, spending that much on a HD now and have most of it empty for a really long time is a waste of money. for motherboard, get one that supports the latest stuff (like dual/quad cores, SATA ,or PCI express) so if you decide to convert it to a top-of-the-line gaming comp, you can without replacing everything. here is a quick estimate of parts and price:
CPU $100
mobo $70
GPU $100
RAM $50
HD $50
PSU $40
case $40
that's about a $450 build for a pretty decent comp