can spend around $400 to start
Stop! No offense but you aren't going to get very far with 400 dollars UNLESS that is for the mobo, ram, CPU, heatsink and MAYBE PSU.....this assumes you have everything else
Especially if you want to overclock you are going to have to get higher quality ram, you will need a more espensive heatsink (the SLK-800 runs around 40 dollars alone), a very good motherboard (too many people overlook the motherboard), and some luck in finding a CPU with good stepping.
I'm not trying to discourage you, but if you are tyring to build a full system with 400 (sans moniter) it is possible - but it will be limited in what you can accomplish (though it would be good for the time being...)
If you do go for a bargain system that can hold its own I reccomend tha Nforce Asus for 71.99 @ newegg (with integrated geforce2), 512 megs of pc2100 ram for around 120 dollars, a 1700+ t-bred (a or b....the As can go to about 1.9 Ghz while I've seen bs hit 2 Ghz) for around 50 bucks, the radeon9000pro for 80ish dollars
That already brings you to 321.99 (or 241 assuming you will use the onboard video)
But if you are looking into overclocking you should try to increase your budget somewhat. But the thing is people don't have that kind ofmoney and its understandable.
But I'm worried you are getting your hopes up if you think that you can spend 400 on a pc (with everything sans moniter) and pump it up to todays standards by overclocking