Mathematica 7.0, plotting x*sin(x), weird looking graph

The command I'm using is Code:

`Plot[{x*Sin[x]}, {x, -80 Pi, 100 Pi}]`

and I get this weird result. Look at x= approx -80 and 130.

http://img504.imageshack.us/img504/5...to100pi.th.gif

Some other similar intervals involving pi also give weird results looking almost like that. There are at least four options:

- I'm too dumb to realize it's supposed to look like that
- My computer is broken
- Mathematica is broken
- It's not a bug, it's a feature.

So my question is, does this happen to anyone else using Mathematica (v7.0.1.0)?