hello, i will be buying a new computer soon. what is the best brand to buy from and what do most top players use?

First how much do u wish to spend ?
I personally build my own is a little cheaper and u get everything you want.
I can reccomend a few things in your computer, and i'm assuming its mainly used for gaming.
A duel core processor amd or intel does not matter.
2 gigs of ram or more .
Now if your buying a regular computer it will not come with a good graphics card built in you will need to purchase one. I buy mine at newegg.com look at the reviews for your price range.
Please go into more detail about what you are looking for so i can really help you more.

Thanks so far! But I will probably be building one via internet, and I will probably spend $750-$1000. How much harddrive should I have if I will be maily using it for WoW and WoW movie making?

You can never have too much hard drive space. 500gigs is cheap get at least that.

http://www.extremetech.com/article2/0,1697,2270998,00.asp
CPU: Core 2 Duo E6550 [$170]
Motherboard: ASUS P5K Pro [$132]
Memory and Graphics: Corsair TwinX 2 and GeForce 9600 GT [$52, $180]
Hard Drive: Seagate 7200.10 160GB [$58 ]
Optical Drive: Lite-On LH20A4P [$30 ]
Case and Power Supply: Cooler Master Centurion RC-534 [$80]
Operating System: Windows XP Home [$75]

Speaking of building of computers ... I can't wait till I got mine done. Still waiting for some parts :D