Taking a screenshot

I have a computer monitor that has both the computer's VGA cable connected to it aswell as my Xbox 360's component cables connected to it. What I'd like to know is if there is any way to take a screenshot of what's on my screen when I'm playing Xbox 360 without the need to buy any software or anything.

Protip:  The real RedCream can spell.  Also, his Firefox very helpfully underlines misspelled words.

There are instances when RedCream adopts a phrasing that doesn't use correct spelling, but we know why he misspells it, to wit:

"i herd u liek mudkips"