So I'm looking to get a computer that I can comfortably play Command and Conquer 3, Red Alert 3, and some Age of Empires 3 on. I don't need a $2500 behemoth, I'm just looking to see what kind of specs I should look for when buying a PC.

I have absolutely no clue about graphics cards, only that ones with dedicated memory are better. Is there a PC that comes with a decent card pre-installed so I don't have to buy/install a separate one myself?

Any advice on what I should be looking for?

I don't know that much about PC parts, but the resolution you intend to play at will make a pretty big difference to what card you require.

Here are my recomendations:

AMD Phenom X4 945 ~ 120-150 bucks
4 gb of ram ~ 100 bucks
Brand name 800 watt power supply ~ 80-100 bucks
Antec full tower case ~ 50 bucks

Now the decision for video card is most important as it will also determine which mobo to get.

For your needs I'd recomend and ATI 4870 + a motherboard that supports AMD AM2/3 socked and crossfire dual video card slots

or

Nvidia GTX260 + Nvidia certified mobo that does SLI (dual video card setup)

ATI advantage is that its cheaper

Nvidia advantage is that it supports 3D vision if you ever want to get in to 3D gaming on your PC.

looking at the games you want to play, any PC that fits your budget should be more than fine... and it'll run SC2 even if you buy it for 10$ in India, so you're pretty much in the safe zone whatever you do.

Good advice, but 800W power supply ? Thats pretty high unless you are overclocking like crazy and running 2 video cards.

For a single video card 550W is plenty. 

Check out this thread, it is a fantastic guide for PC specs.

If you don't plan on building it yourself, you'll still get a good idea of what you should look for and need.  I recently built a pretty good PC for $1500 CAD after tax;

core i7, Radeon 5850, 8GB RAM, 1 TB HD.  You can get good dollar value if you build it yourself

Thanks so much for everyone's help!

I don't plan on building it myself (I know, I know, I'm a poor excuse for a gamer.) But if I can play those games on medium resolution without having to restart my computer every 15 minutes, I'll be a happy guy.

So do you think it's do-able on a $600-$700 budget?

If your only planning on playing C&C3, RA3, and AOE 3. Then a bugdet of 600-700 is not hard. You could probably play high res for the most part. Though the better question is are you including a monitor in this budget or not?

http://www.techreport.com/articles.x/18510/2

Check out Tech Reports $500 system. Add a little more ram and Windows and you're done.

I'll say, go to newegg.com check out their prebuilt ones.... but if you're gonna PC gaming you gonna have to upgrade the graphics card sometimes.

No, the monitor is not included in that budget. I have a 32" TV I can hook it up to.

@Dogswithguns: You're right, but I want to delay the inevitable for as long as I reasonably can on a less-than-ideal budget. haha.