Sure man.. I can suggest a few things. First off, I suggest shopping at NewEgg. (
www.newegg.com) Great prices and great shipping.
With that budget I would start with a AMD processor.
AMD Athlon 3000+ XP 154$
http://www.newegg.com/app/ViewProduc...103-381&depa=1
ASUS A7N8X 78$
http://www.newegg.com/app/ViewProduc...131-455&depa=1
MSI Radeon 9800 Pro 195$
http://www.newegg.com/app/ViewProduc...127-127&depa=1
Corsair 512 PC3200 DDR Ram 79$
http://www.newegg.com/app/ViewProduc...145-026&depa=1
Western Digi 120gig HD 85$
http://www.newegg.com/app/ViewProduc...144-118&depa=1
Antec 430w TruPower PSU 69$
http://www.newegg.com/app/ViewProduc...103-908&depa=0
TOTAL=660$
The case is up to you man.. its all preference (get one without a PSU, you want that antec)
These are just my suggestions on how I would spend the money.