v8700 run at about 80Mh/s, so you'd get about 2.4GH/s, which is about the same as you'd get from 4 HD6990s, but obviously with no investment. if you're going to do it (be prepared to lose your job), I'd say the way to go is a linux boot image. If you can customise it to auto run the miner and then just reset the machine and pull out the usb to set it back to how it was, you'd be laughing...