YES... you can use two (or more monitors) at once. I have four 20-inch monitors hooked up to my desktop... sometimes I surf the web using ALL monitors.
Back in 2004 when I installed a Geforce FX 5500 and hooked up two monitors, I have never gone back to using just one. Using more monitors speeds up my usage (it limits the number of times I have to minimize/switch between open applications). The multi-monitor technology extends the desktop view.