Will this air compressor be sufficient for cleaning out a PC?

I don't think so, not for the price. Airbrushes like that don't move a lot of air, they just lightly 'puff' the air. My cousin used something similar for her makeup and she was able to hold it within a few inches of her face with no trouble. Air cans have a lot more force.

You might be better off with something like this
http://www.amazon.co.uk/dp/B00R1LP3B2?psc=1

The other options that I know of are datavac's and canless air dusters like the 02 hurricane but both are around 70-80 pounds or more (sorry don't have the sterling on my kb).