Flyboy pretty much covered it, but I thought I'd put in my $0.05 (Canada got rid of the penny...
). I've had gaming desktop computers for more than 10 years now. When I was at the height of gaming, I was on a four year cycle with computers and a two year cycle with video cards. This is not entirely necessary, of course... I just tend to put a lot of money into my computers because I spend so much time on them.
My current desktop computer I bought in January 2010. I just replaced the video card a few months ago. I expect it'll last another 2 years for me, at least. Probably more because I don't necessarily play the latest and greatest games graphically immediately anymore, and graphics technology isn't increasing exponentially the way it used to... and a lot more of that is built into video cards.
Which brings me to: I usually spend about $350 to $450 on a video card. Yes, you can buy a $150 one, as Flyboy suggested, but while it'll run really well now
, it will not have much of a lifespan. Video cards are IMO the most important component of a gaming computer, so don't skimp here. And the best thing is, if you buy a whole new computer down the line, you can (almost always) reuse your video card if it's still new/good enough. When I look for a video card, my basic rule of thumb is to get the second-most expensive/newest one. Sometimes they'll come out with a super l33t awesome new model that's like uber expensive, and then shortly after come out with a 'budget' version with most of the features but not quite as a high specs - I'll get the latter. I've used both nVidia and ATI/AMD, and there isn't really any major differences. Right now I have a GeForce GTX 670, and it is amazing. Again, it's your decision, but to me it is worth it to spend a little more on video card.
Re; HDs, I have a 160 GB SSD for my 'C' drive. (This cost me nearly $500 back in 2010, lol. I wanted the 80 GB one but it was on backorder, so for some reason I coughed up the money for the 160 GB, heh.) It stores Windows, my regular programs (browser, Office, etc.), and non-Steam games I play a lot (eg. SWTOR). Everything else goes on my 1.5 TB secondary drive. Programs almost always give you an option where to install them, so what I do is just change the drive letter when installing. Haven't had any problems with this setup. Regular HDs are cheap, so get way more space than you think you'll need.
Re: cooling, I've never used anything more than fans. I have some some heat issues in the past, but my computers tend to reside in cold basements so that helps.
I find that if they are properly ventilated (ie. not
put in those little desktop PC cubby holes in the big fancy office desks), you don't necessarily need extra cooling. They get noisy, sure, but fans are cheap to replace when they break. However, a cooling system is never a bad idea, especially if you live in a warm climate. This is greatly dependent on your case though - if you get a case designed for gaming, it'll have more ventilation built in and you *might* not need anything extra.
Comments on Flyboy's post:
As Talo said, a desktop is the best for gaming. You can get gaming laptops but they cost a fortune and you can't really upgrade them. I personally love having a desktop because its very easy to get new components and they have far better performance (no need to balance power with battery life like on a laptop). I'd also recommend home-building it if you can as you'll get much better components for a better price if you do.
This. You should only consider a gaming laptop if you are away from home a significant period of time, and do a lot of gaming (or want to) when you are. I got an awesome expensive gaming laptop last summer... but I also have a lot of discretionary income at the moment.
And I do spend quite a bit of time away from home, and my husband makes use of my computers for gaming too.
You could if you really wanted double-up on the graphics card using SLI (NVIDIA) or CrossFire (AMD), and this will improve performance as one graphics card can handle graphics processing whilst the other does physics, however my PC does just fine with one card and honestly I wouldn't recommend it unless you want the absolute best graphics (after all, 2 cards will produce extra noise and heat). It also limits your choice of motherboards and cases as you need a motherboard with 2 graphics card slots and likely a full size tower-case capable of holding such a long motherboard.
The only person I know who uses dual video cards is my brother, and he does computer graphics research for a living.
So yeah, IMO not worth it unless you are always buying the best video card out there.
One other thing to note with RAM is that if you have 4GB or more of RAM then you must get a 64 bit operating system. 32 bit operating systems can't handle more then 4GB of RAM, so anything above that is wasted on them.
I highly highly recommend going with a 64-bit system, for this and other reasons. Almost every reason for sticking with 32-bit (ie. compatibility) is not an issue anymore. The only time you'll come across it is if you try to play REALLY old 16-bit games. (Even then there are workarounds.) 64-bit is new standard, get it.
Personally, I'd say go for Windows 7 (Home Premium will be fine), however if you feel you can get on with the Windows 8 'Metro' interface then it'll be just as fine (and not to mention about 1/3 of the price). We can't really help you with this bit as its more personal choice (since Windows 7 and 8 have more or less the same performance and the same features).
One more thing I want to mention quick is a rough price estimate. I don't know exactly what prices you're looking at for components as I only know UK prices, but at a guess I'd say you're looking $500 - $700 to get a desktop machine at the specs you want, twice that if you want the equivalent laptop. And again, you'll get a better deal if you home-build, but you will be able to find pre-build machines with the specs you need if you're not confident enough making your own PC.
For comparison, I usually spend between $1500 and $2000 on a new gaming PC (including taxes), but I know things are generally cheaper in the US, and I certainly go all out in certain areas (eg. video cards). And I usually let my brother talk me into getting components that I don't *really* need, haha. The flip side is my computer runs amazingly for years and I don't have to worry about it not running some new game that comes out during that period.
I definitely second building it yourself. That way you get the most say on all the components. A lot of pre-built computers will skimp in certain areas to keep their prices low, but as a result you don't get the performance you could, or it doesn't last as long. That just seems like a colossal waste of money to me. Personally, I buy my computers at NCIX.ca
- I can choose all the components separately and they are priced separately, but they will assemble it for me before shipping. There is undoubtedly somewhere similar in the US (NCIX also has a US site, don't know how their prices compare though). Or you can shop around for each component separately and put it together yourself. If you are willing to put in the time, you will likely be able to save quite a bit of money that way. For me, I'm willing to pay for convenience.
As a final note, make sure you invest in a good gaming mouse with extra buttons. In Canada you can get them for $60. It is worth it. I like Logitech mice, personally. Gaming keyboards are nice, but not necessary unless you have extra money lying around. But you can always pick one up later. That's the best thing about desktop PC gaming (as opposed to laptops & consoles).
Good luck! Let us know what you go with or if you have more questions.
PS: Alienware definitely has style, but is SO cost-ineffective that I'd never consider them.