Hp desktop 1640n no signal to monitor.
Suddenly show this error in monitor.It work well half hour ago.Psu seems well;fans runs,leds on except the hard drive light not on or flashing and hard to feel it is turning or not.this monitor work on other computers and the connection cable also showed nothing wrong.The cd/dvd open and close well.I insert the system restore cd it runs but no boot up.What are the problems which parts I should looking in? Hard drive? Vedio card,or mother board?Since I do not have those parts can be change and try at hand.Please tell me what should I do next.I have the backup external HD for this computer.How can use it to take over the bad HD.Please help.This is 6 years old unite and work well for years except change PSU 6 months ago.