Bitcoin mining is no longer feasible with even such high end hardware as yours. It nowadays requires special ASIC mining equipment. The performance of the connected miners is measured in Hash per Second. This means how many hashing operations of the kind required in Bitcoin is the equipment capable of doing per second. The fastest ASIC mining units currently produce a couple of Terra Hash per Second, while your graphics card will not be able to output more than a couple of Mega Hash per Second. If you have to pay for electricity, this means you will never make any profit, so go figure.
When mining bitcoins your are just randomly searching for solutions of a cryptographic puzzle, that is designed to take the whole network about 10 minutes to solve on average. There is no guarantee on how many Hashes you need to calculate, before finding a valid solution. This only counts when solo mining however. It is therefore strongly suggested, that you join a pool to make any profit. A pool distributes the work to solve the puzzle to its partakers. When pool mining, the pool can calculate your estimated income based on your share of the total hashrate of the pool.
If you want to mine with your gpu, there are 100's of Altcoins that support GPU mining and are still somewhat profitable to mine.