Dell PC No Signal Monitor Keyboard or Mouse

I've got a Dell Optiplex PC that was working just fine until the next morn I turned it on and the monitor only displayed "No signal." There also isn't communication with the mouse, keyboard or wireless adapter. No new software has been installed. Tested the monitor on another computer and it works fine. I've unplugged all items and restarted to see if it would reset. Tried new cords and that didn't work either. Tried the simpler things first. The computer does come on, you can hear the fan running, but there are six beeps. OS is Windows XP. I would appreciate someone else's insight. Thanks !

Are you able to boot into SAFE Mode? ______________________________ If you can get into SAFE Mode, consider rolling back to a Restore point one day prior to the beginning of the problem. Graphics Adapter or RAM memory is what I'd check next, if unable to boot into SAFE Mode. You'll need to be able to boot from a CD, to test RAM with either Windows Memory diagnotic Memtest86 ______________________________ do you have another video graphics card you could swap in?

Just to add to the excellent information provided by Doug, 6 beeps on startup often indicates a keyboard error….this can either be the actual keyboard itself ie a sticky key or other physical fault, or a fault with the keyboard controller (electronic bits on the motherboard)

Try another keyboard and see if this helps, although they are cheap to buy, just borrow one for the test.
More information from here:
http://www.computerhope.com/beep.htm
Good luck
Regards
paws

THANK YOU! I disconnected all cables and then reconnected each one by one and the computer started right up. In the process I was informed by the user that a new printer had been installed. Thanks for your help!