I have a Dell Desktop PIV Professional SP 2 version,
I was running Aqua desktop and all of a sudden desktop
display gone blank. Tried several ways no joy. Getting
a warning message as security setting not set for Active x
hence the problem. Trying for safe mode but F8 not
responding. System is healthy otherthan desktop display
problem.

Have you tried increasing the screen's refresh rate? (I know it's simple, but I'll help you more after it)