I've been mining my two computer GPU's on this site with averages of 11MHPS on one and 30MHPS on the other.
If you want to mine bitcoin you need to buy a modern bitcoin ASIC miner. Today 1000 GH/s is extremely slow and the fastest miner, I believe, has 16000 GH/s (16 000 000 MH/s).
There are some altcoins you can still mine with a PC. Some services let you mine altcoins and get paid in bitcoin.
At Bitminter we only support bitcoin mining (with merged mining of namecoin). Maybe we'll support other coins in the future.
Thanks for the reply. I didnt specify but i'm mining bitcoin on both computers, but found it strange that Bitminter had two GPU's running for two weeks and only paid out a small amount while the CPU mined bitcoin at Nicehash for two days and the pay out was 3x or more.