Dell Inspiron 1545 :: Instead Of Typing Computer Perform Random Tasks

I own an inspiron 1545 which works properly for the most part, except for a small, but annoying problem. Sometimes, when I type, instead of characters or numbers appearing on the screen, the computer would perform random tasks like try to open a file when I press O (and I am not holding down the Ctrl key), save my work when I press S (again, no Ctrl key), and change my typing language. It used to run on Vista, and was recently upgraded to 7, but the problem persists.

For example, typing the word 'frustration' would sometimes lead to this:

frustrati (Open dialogue box appears)

It's especially annoying when it changes the typing language mid-sentence.