Take your pick, Dell, HP, get a Mac if you want. I can't really direct you here because I would build my own
You're going to get a more personalized one that fits your needs and it'll also be cheaper... only difference is instead of having an instore warranty you have a warranty for individual parts.
Just look through some of the sites, they all have good prebuilt computers. If you do think you might want to build your own computer I'm sure there are TONs of videos on Youtube!
Either way, you'll need a price range before you start looking. Computers get better and better... and more expensive real quick.
I buy a majority of my parts from Newegg. Here's their desktop (prebuilt) PC section.
Newegg.com - Desktop Computers, All-in-One PCs
Has all the brands there..