Acer 3690 hangs with black screen

That is your windows explorer hanging. Try going on safe mode (pressing f8 during initial boot) then system restore. See if that helps.

may be hard disk has over loaded or virus

The partition D is actually a back up partition that has factory image for the original Operating system that was installed in the computer.
factory recovery ( DATA LOSS )
if the computer is booting to windows, then click start and open a folder named as 'acer' listed in ' all programs '.You will find the ' Acer e-recovery managent ' in that folder.You can open it and click allow for the user account controls.Please click 'restore ' for the next screen and the select the first option, 'completely restore to factory defaults '.Follow the on screen instruction to initiate the Recovery.
The Alternate method for starting the Recovery on startup is using the combination of ALT+F10 ( some models its ALTgr ) on startup.Press and Hold down the ALT( Left hand of space ) and at the same time keep on tapping the F10 key till you get the message " Windows is loading files".Just follow the On screen Instructions to start the Recovery.

It sounds to me like your screen has gone and needs to be replaced

My dear friend as I told you that you should change your RAMs it will b ok give me your response on [email protected]

your computer needs a fresh slate. insert the operating system cd's/cd and restart the computer. follow the on screen instructions to install a fresh operating system. make sure you back up your files first. thank you for using fixya

Yep, actually, that was what I was going to suggest.

If your booting to the splash screen ( ACER Logo screen ) then it goes black reboot - access the bios and do a bios hdd test - you mostlily find your hdd has died. Head scrash

hi
do you have the power saving settings to switch laptop off after a certain lenghth of time?is the laptop overheating?are you using it on a soft surface eg deep pile carpet?

Hold crtl+shift+esc and tell me the list of everything under the processes tab.  You can resize the task manager window til it shows all of them without the slider.  Hit Ctrl+Print Screen to copy your screen.  Then start run mspaint and hit Ctrl+V to paste it.  Save it on your desktop as rscraig2screen.jpg and post the image on my google group.  Click +add file next to Files.  It will tell me when it's loaded.  Have you run spybot or AdAware(NOT AdWare!)?  Do you have an integrated video port or is it a card?  
James Mac