I have looked at buying some used GPU's and mining litecoins, is this likely to yield a profit or is it dependant on the possibilty of litecoin value increasing?

hi all,

I am thinking of getting into bitcoin mining, I have a spare old dual core pc and I live somewhere with free electricity, so would it be worth it to get into bitcoin mining? And if so, what gear should I use? is it worth investing in something like a couple of the @block eruptor USB ASIC devices?

thanks