Why does my keyboard's mouse keep dragging things and highlighting them blue on its own?

My netbook’s keyboard mouse keeps highlighting things and dragging them, on its own. It doesn’t do it all the time – maybe 50% of the time. It’s very annoying.

I tried googling for a solution, but was brought to all these weird sites with a bunch of speculations.

The netbook is about a year and a half old. I have found that they last about two years and then I tend to have to replace them.