Here's your best bet IMO:
http://www.newegg.com/Product/Produc...82E16813157125 http://www.newegg.com/Product/Produc...82E16820145040 http://www.newegg.com/Product/Produc...82E16819103243 http://www.newegg.com/Product/Produc...82E16811138065
Including shipping, you can get the above for $191 and maybe a little less if Newegg gives you a break on the shipping. You will need to use your existing hard drive, DVD drive, keyboard and mouse. Later you can add more memory but if you run XP then 1 gig should do OK. You might get by with the motherboard's on-board video until you can buy a better video card. Also, the motherboard I specified will let you upgrade to AMD's three or four core Phenom processors when they get to be dirt cheap in a year or so. The weakest link of all these parts is the 430 watt PS in the case but on your budget you have to make sacrifices.
This isn't too bad for a complete system but it exceeds your budget:
http://www.newegg.com/Product/Produc...82E16883103135
I too agree that your options are limited and you might be better saving more and getting something later.