Billy,
The advice given to you so far is spot on. As far as your last question goes, you're mostly paying for the name when you buy from the major computer companies. These days all the parts are the same and come from mostly China, Taiwan, Thailand, Japan and Korea.
If you are not computer savvy, or 'just want it to work' without building it yourself, then a pre-built from one of the major outfits is your best bet. Your OS choices are limited as most of the widely used software is either PC, Mac or Crossplatform (PC & Mac.) Either is fine as once you are working within the NLE/Graphics software itself, your OS is only there to support the software anyway.
Your gripes suggest you are budget concious so you need to ask yourself these questions;
1. What am I planning to do with my prospective computer? If you're just planning to make home movies or 'YouTube Specials', then you absolutely do not need the latest/greatest/most powerful unit known to man. Do some research as Gldnears suggested into both the software and the camera you'd like to use to see if they meet the minimum requirements and whether they are compatible with each other and the computer.
2. How much am I willing to spend? As I mentioned, name brands cost name brand money. Often you get what you pay for, but there's always the possibility of getting 'lemony fresh' gear that will cause you endless hours of 'enjoyment' and expense as you deal with tech support. If you go with Apple, they are the only licensed distributor of the mac computer line so you'll be dealing with either the Apple Store or Best Buy on the consumer end. On the PC side, there's HP (stay away from the Compaq line trust me), Dell, Acer, Gateway and a bunch more than I can think of at the moment. Reputable places where you won't get the 'song 'n dance' to get you to buy extra stuff you don't need are Tiger Direct and Walmart. TD has excellent tech support but with WM you'll have to deal with the manufacturer. The good thing about WM, is you can go to the store and get a hands on look before buying.
3. Am I going to be able to make this thing worth what I paid for it? Upfront, if you're looking to make a living with your intended computer (wedding video, etc.) then you have the potential of making back the money you put into the purchase price. If you're just doing this as a hobby, can you afford to blow a ton of cash on something you're just going to fool around with?
No matter what choices you make or the reasons you made them, when starting out keep it simple and keep it cheap. When you gain greater proficiency and knowledge using these tools, you'll be in a much better position to recognize where your limitations are and what you'll need to get to the next level.