Normally that is because the monitor is not plugged in. Check if it is well connected. If it is well connected, try another monitor. If it does the same thing again, come back here for more info. Be sure to explain everything that happens when you start your PC, like if there are beep patterns that could indicate anything. Does your PC make one beep at startup? Does you PC stay on?

Yep it all works fine fans start all connected fine the normal one short beep start up. Lights on front flash.

P.S Someone said sommin bout a Light on the motherboard but cant see one
Thanx Mike

Hi mike_webb55,
Check for the latest video drivers (for monitor) & re-install. "plug-n-play" is sometimes called PlugNPray because some monitors just won't work with some system configurations.. no matter what you do.
If that doesn't work..
exchange your monitor for a different brand.
Hoope this helps
RGPHNX

I im not 100% shure what your on about but how can i do this if i cant see what im doing on the screen

Have you connected another monitor to your pc? If not you should try that because if another monitor works, you will know that the problem is the monitor.

Ive connected another monitor to the tower and when not tunned on it says no signal but when turned on the notice is removed and only a blank screen is visable.

If you are sure this monitor works, shows blank at startup and you get one beep, the chances are that your video display circuitry is defective. Your video card is probably a dud. If you can, try another card in your computer.

Im a total noob about computers but here is wot i have experienced with my system. I was playing a game and suddenly every thing went of on my computer and i got no signal on my screen so initialy i unpluged the monitor cable and replugged it back in and still didnt work altho i had power to my fans and there was a beep. In the end it turned out that my PSU had blown but i was still getting little power just to my fans and lights i changed my psu for a bigger wattage to 550 watt and sure enuff every thing came back on maybe u could have overloaded your psu i really dont know but have u heard about something called a D-Bracket it has lights on and displays certain sequences which show a diagnostic of your start up to show u wots functioning properly hope this helps

was the screen completley blank or did it say no signal