Thanks for all the replys! Guess I'm late to the party once again   

Approximently how long will these 1800 blocks last and how long do you think it takes for the difficulty to increase beyond 2 million?

Greetings, I'm planning on purchasing a dedicated mining-rig but first I would like to get a hint on how much money it will generate and if it will cover the costs of the machine itself.

Components:

• CPU: AMD Sempron 140 2,7GHz = 44$
• PSU: Fractal Design Newton R2, 800W = 187$
• RAM: A-Data 1024MB DDR3 = 17$
• MOBO: ASRock 3N78D = 76$
• GPU: XFX Radeon HD5970 Black Edition 2GB = 570$

Total: 894$

Other information:

• I will get electricity for free so the electricity costs is out of the picture.
• I will be using Ubuntu as OS.
• I will probably be overclocking the GPU.
• The machine will be running 24/7 for three months.
• After the three months I will be selling all the bitcoins I generated through Mt Gox.

So, will three months of mining cover the costs of the rig (894$) or is it just a waste of time and money?

/Kubba