In which case you're not running at 30-70fps, probably closer to 20-30 when you average things out.

Put simply, it is physically impossible for a monitor to deliver more frames per second than its refresh rate allows for - so if your monitor only runs at 60hz, you will only ever get 60 frames per second, regardless of what any FPS monitor reports. If you force the frame rate any higher than that you'll get image tearing, which is what the V-Sync option is for in most games - it binds the maximum frame rate to the monitor's refresh rate, which eliminates image artifacts.

Or you have a monitor that can handle 120Hz. But still, no matter what, you have to admit that you will get less video lag if you have a higher fps.

If what your talking about is the slots behind the computer thingy... Than I have like 5.

On your mobo you should have a specific slot known as a PCI-Express x16 slot. It looks like this...
Big Enough?

Yeah. I have one of those.....

What is your current video card?

GeForce 6150 LE... It came with the computer. How bad is it?

Umm, it's integrated so we can assume it ain't that great.

Not necessarily. Lag can be caused by anything from a CPU bottleneck, to insufficient memory, to slow HDD access speed; it's not just a graphics related issue.
Very.

Sometimes, but if you compare the difference between 30fps and 60fps, you will notice a considerable difference in the amount of video lag you get (To demonstrate, see attachment. Old runs in 640x480, and the beta gives you a little more options. Thank Koroush Ghazi and his Tweakguides for the links.). I agree that most of the time 30fps is more than enough, but if you ever get into a large scene with a lot of action, that number will significantly decrease, so I feel it's better to have a higher fps to expend in those situations. P.S. to confirm Rookie's statement about tearing: up the fps above 70 on the 2nd screen of the beta.