At twelve megahashes per second, and the current difficulty, yes - give up.
I normally wouldn't say that because I can put myself in your position, and I would want to put my hardware to work no matter how shitty, however with the current difficulty it would really take you quite a while to make one.
If you don't take my advice and give up (I sure as hell wouldn't if it were me, but I'm stubborn as a fucking goat), then use UFASoft's SSE2 CPU Miner for the CPU, and the CUDA miner for your GPU.
Set the CPU to "low" priority in the task manager, and the CUDA miner to "above normal" - that way the cpu being clogged won't starve the GPU of work.
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