My Dell Inspiron 7000 will not allow this! I read a few fourms and complaints about this very issue without a clear answer on how to fix the problem. All my drivers were totally upto date and this was a brand new fresh system. After 3 deays of frustration and trial and error I solved the problem. It's to do with the smart start feature in Windows and the Intel Fast start.
Here are the steps to fix this issue:
In task bar click the "inter Rapid Start Technology" icon.
Go to Control panel, Hardware and Sound, Power Options, System settings and set it as below.