Help with sleep mode

If I lock my computer (or leave my computer for 5 minutes to lock automatically) and turn off my monitor when I come back after a long while I turn on my monitor and nothing will show up. My tower's power light is on so I know my computer is not off, yet even after moving my mouse around and the colour of the light on my tower and monitor changes from orange to white, nothing is displaying. The monitor does not say it's not connected, or the message that it is going into powersave mode (message given when my computer is off) so I know everything is working fine. I assume my computer has gone into sleep mode, or whatever this mode is called, but I have no clue how to get passed this except by holding down the power button on my tower and then turning it back on.
Any help is appreciated, thank you.

I'm new to these forums so I kind of skipped over trying the search feature, although once looking at my question again there are a list of related topics that may help me, sorry for posting something already discussed.

hey this happened to me too! i can't seem to wake it up! I pushed a lot of buttons on my keyboard, and moved my mouse here and there. The computer still won't wake up =/ ANy help would be great