I have a compaq as well, you have to hold the FN button (next to the ctrl button) and then press the home/prt sc button. Then just ctrl V in paint or so and cut it out and well follow the tutorial from there one ^^ good luck!
maybe you have to hold the FN button and the Prt Scr button at the same time? i don't know i don't have a toshiba, but you can google on toshiba printscreen you will find it then i think.