Cant wake computer from sleep or reboot

Flash your bios

There are options for what devices will wake a system from sleep. I personally turn off the mouse -- I don't like vibrations moving the mouse and starting the system.

Did you try holding down the fn+f2 combination or the 'windows key' or just 'function key' for a count of 5 ? Then release. Then wait 30 seconds while video gets itself together.

From: http://support.microsoft.com/kb/266283

" Open the Keyboard control panel item, as described in Method 1.
Click the Hardware tab, and then click Properties.
Click the Change Settings button

Note This step requires Administrator access
Click the Power Management tab, and then verify that the Allow this device to wake the computer is enabled.
Click OK, and then click OK again."

Also, very rarely my PC will come out of sleep but my samsung t240hd monitor (which I love because its 1920X1200) doesn't detect video signal until i cycle it through the it's input options.