HELP!! Dead Computer

[JoeRedskin]

So I went downstairs this morning and turned on the computer. Nothing happens. Plugged in, hooked up and nothing. Green light on back of comp lights up so it is getting power, it just wont power up.
It's relatively ancient and may just have given up the ghost but it still has data on it that i will want to retrieve (though most of the important stuff is backed on external hard drive). I have three questions:
1. Any suggestions on getting my old comp running?
2. If not, how do I get data off of it given it wont power up?
3. Any suggestions on a basic desk top in the $300 to $400 range? Been awhile since i bought a comp so I dont even no what to look for or where to look for it nowadays. Kinda need it ASAP.