If you want a desktop system, and you want to customize your build, go with a Dell. User friendly website. Cost comparison builds. Upgrade or downgrade options.
If you want a system that is quality for a decent price, Emachines is a brand I have had a lot of good experience with.
For Laptops and customizing, again, Dell would be a good way to go. Other known good quality brands are Acer and eMachines.
Stay faaaaaaaaaaaaaaaaaar away from HP.