I have approximately 2.5-2.6 G/hashes between my systems.  I can reasonably expect to average 1.5ish BitCoins per day.  You would be lucky to get 0.5% of my hashrate, even with one of the best 4000 series video cards.  I don't intend to discourage you, but unless you have a 5700/6700 series or higher it's probably not worth the cost of electricity and you could expect to lose money in most places (depends on your electricity rates).