Paying a portion or paying all of that loan with credit at 0% APR. Afterwards reinvesting it to performing stocks or forex before the 0% APR switches to a fixed or variable rate???

Anytime you can borrow money for a lower rate that you can invest it at, it is a good idea....just ask any banker. One thing to watch is the fees from the loan and balance transfer. If all of the fees add up to more than 2%-3% of the loan amount then this idea will be a little riskier and not as profitable. The key is making sure that you pick a solid investment. Unless it is a governement bond or other riskless investment, there is no way to be sure that you won't lose some of your money and have to cover the rest to pay back the loan when it switches to a higher rate. It is definately a gamble, but could be quite lucrative if done correctly.