Can i use two monitors on the same computer?

Or do i need two graphics cards?

After i connect them how do i switch bewteen the monitors and choose what to display on each screen?

Nope, no new drivers should be needed, I'm pretty sure it's windows itself that handles it if your card is capable.

One screen is considered the left screen and the other the right screen. You can move your mouse between the left screen and the right screen via the border in which the two 'touch', so the right side on the left screen and vice versa. You can maximize a window in each screen independently, so you can have like, Microsoft Word on one and Internet Explorer on the other. Just drag the window over and maximize.

I would use the lates drivers of your card. The application that handle those feature is part of your driver's installation.

You wont break anything by trying it out.

If you use the "extended desktop setting" the maximized window will only fill one of the two monitors.

But again, be adventurous. You wont mess anything up...

With a 8800 nvidia card, download the latest drivers, which you would do anyway.

Right click on either display and select the nvidia control panel. Select the option to configure multiple displays. I think you will want "dual view".
With dual view, both monitors look like one large monitor. You can drag a window from one to the other, and do anything you could on just one monitor. When playing a game, the only main monitor will be used. There may be some games that can use multiple monitors.

I will leave my e-mail up along with some performance monitor on one display while playing a game. If I need to break out of the game, I press the windows pearl button, the game is suspended, and I can do anything I want before resuming the game.

Dual monitors is one of the best things around.