I need a new computer, any advice? (lots of info given)?

So my current laptop is 6 years old and was bad when it was new, I don't want an upgrade to this computer, but a hole new computer. So, I don't know what to get. I want to stay around $500, and I don't care whether its a desktop or laptop. (note that I do not have a monitor, so that is included in the price.) I do have an old computer tower case, so I don't need a new one. I want to be able to run minecraft smoothly (very rare lag), and other games (Portal, G-mod, terraria, castle crashers), at a reasonable frame rate.

that's pretty much all there's to know. And the cheaper the better (I have to get all the money myself, and I have no income). The more information the better.

-thanks a ton!

Added (1). I don't know where David got his info, but DvD burning is NOT a primary use of my computer…

Will this graphics card be sufficient for a gaming computer?

I have heard that with gaming, the graphics card is the most important part of the build. The one that I got suggested to me is Asus AMD Radeon HD 7850 DirectCU II Graphics Card (2GB GDDR5, PCI Express 3.0) . Is this card good enough for games like Battlefield, Minecraft etc. On high settings? If not, it would be greatly appreciated if you could suggest one.
My second is that I have been getting my parts off of Amazon. Is there another trustworthy UK website, that I could buy the parts from cheaper?

What Computer Should Be Good Enough To Run Minecraft?

Can someone tell me if this one would get it to run decently with little to no lag? Http://mobile.walmart.com/m/phoenix#ip/HP-Black-Licorice-15.6-2000-2d29WM-Laptop-PC-with-AMD-E2-1800-Accelerated-Processor-4GB-Memory-500GB-Hard-Drive-and-Windows-8/28503696?type=search

Transfer Minecraft worlds from pc to mac?

I want to transfer my minecraft worlds onto my mac (I originally had a pc) but i don't know what folder(s) i should save my worlds to. I downloaded the game, i put my minecraft worlds into my flshdrive if this helps. I'm also logged into mine craft.

Also someone had told me that i need to install something called "Explorer". I'm wondering if that means internet explorer. If anyone knows, that would be helpful.

Laptop computer unexpectadly turned off?

I was on YouTube and minecraft, then i got blue screened. It went away, then i got asked to start windows normally. It said problem with something within the computer but i don't remember. What could be causing this? I did play minecraft for quite awhile yesterday. Also i downloaded pictures fron google yesterday, so what might it be?

What should I buy to increase my FPS?

I was browsing ways to see how I can increase my FPS for Minecraft. I want to buy something that will add on to my computer to increase my FPS. I want to get at least 150 FPS and in a budget range of 300$

My friend told me I should get an Intel Core i5 but I don't know if that will increase my FPS or not. What should I buy to increase my FPS?

Price of DayZ Standalone?

Ok so… I know it costs about 30 bucks right now. But I also know that Dean Hall said that he wanted it to be like minecraft and his expected Beta price was like $15? So basically, what do you guys think: Snag it now while it's cheap? Or wait for beta to see what the price does? Either way it's a great price but I like to be cautious with prices when I think they're going to drop.

How to Make MineCraft Faster?

So I have a Dell Mini laptop {Windows XP} that has Windows 7 Starter pack on it. It also has Service Pack 1, and is 6 years old.
I'm trying to find out how to make MineCraft work a little faster on it. I'm not sure if its because its such an old computer, but it just lags out all the time.
I've tried almost everything, giving Java more memory, giving me more RAM, deleting tons of pictures {486 to my hard drive!}, deleting unused apps, getting the latest version of Java constantly, updating my antivirus packages, but nothing works.
I'm probably going to get a new computer soon, but I was just wondering if there's any hope for my old one.

I can't use my keyboard and CLICK with my mouse at the same time?

When I'm using the WASD keys to move around on games such as minecraft, I can't click with my keyboard at the same time, for example, if i'm moving to the right, i can still move my keyboard but i can't click with it until i've stopped. This is very fustrating, can anyone help?

Added (1). this is a laptop

Why won't minecraft allow me to purchase it?

I went on to the minecraft website I made a Mojang account completed step 1 and 2 my community name had a tick on it but when I clicked purchase nothing happened only it went a lighter green when I clicked it, it didn't bring me to the download part or tell me what's wrong and my credit card details were correct