Depends on the power draw and how much you pay for electricity. If it's a Nvidia card, I can answer pretty quickly: no.
Going to be a very low payout, right now. Truth is, while the value of BitCoin is so low if you're paying for power it's very hard to make a good income.
Two things I can recommend:
1) I built a small solar farm to power my two miners (the solar panels cost more than the miners themselves, but here is Australia electricity is actually a bigger cost than the actual hardware). That brings the break even point back by about 6 months
2) Look into time based metering of power. Some electricity providers will install a smart meter which then records how much power is used when and gives you a much cheaper rate between say midnight and 6 am, sometimes a tenth the rate. Mine then!
My instinct, though, is that 100 Mhash is going to earn about 1 bitcoin every, what, 4-6 days? The return is almost negligable
unless there is something specific you want to buy with BTC, at which point mining is cheaper than buying BTC every day of the week.
Hope that helps!
