INSPIRON 640M WILL NOT GO INTO SAFE MODE , IT GIVES OPTIONS BUT NONE OF THEM WORK , THEN IT GOES TO THE BLANK SCREEN.

Try going to safe mode manually. The steps mentioned below will help you accessing the safe mode

Step 1: Shut down your PC completely.
Step 2: Turn on the Power button.
Step 3: As soon as you turn it on start hitting the F8 key on your keyboard until you get to a black screen called "Windows Advanced option". (If you don't get to that that screen but you end up reaching the blue screen than that means you have delayed in hitting the F8 key. start again from step 1.)
Step 4: As soon as you reach "Windows Advanced option" use your down arrow keys to choose an option called "Safe Mode/Safe mode with networking".
Step 5: Select that and HIT ENTER.