Are you able to try the keypress combination with an on screen keyboard to see if the unit is actually registering you pressing both keys at the same time ? I actually use eurosoft pccheck and test outside of windows.
Will be interesting to find out if its windows 7 causing you troubles or hardware, updating the BIOS of you unit is always good to do, should be v2.04 if it is not then download from Link Removed and install, please make sure you have the mains power plugged into the notebook when updating your BIOS.