How do i change screen brightness dell optiplex 960

What happens when you restart into SAFE MODE? Click on START button While HOLDING SHIFT KEY DOWN Click on RESTART

How to enter BIOS?
1. Turn on or restart your computer.
2. Press "F2" to enter "System Settings" (BIOS) when the DELL icon appears.
Restore the BIOS to default settings.
Press "Caps Lock", "Num Lock" and "Scroll Lock" buttons to light up the corresponding lights on the keyboard. Then, press the following three combination keys:
Alt+E - Clear (Release) the interrupted resources and reallocate resources at next startup. After pressing the combination key, you will hear a sharp beep tone.
Alt+F - Restore BIOS to the default settings. After pressing the combination key, you will hear a sharp beep tone.
Alt+B - Restart the system.
Password clearing method 1: When the password input box appears, type in the password and press "Ctrl" and "Enter" simultaneously.
Password clearing method 2: Remove the PSWD jumper on the MB and start up the system. Set the password to empty in BIOS, shut down the system and reconnect the PSWD jumper.
Hope this method will help you otherwise check Dell Optiplex 960 Manual- https://guideusermanual.com/product-name-optiplex-960-manual&po=344822&lang=English for expert's suggestions.

Log in to: http://www.dell.com/support/home/us/en/04/product-support/product/optiplex-960/diagnose and send this info to Dell. As I recall lights 2,3,4 are either memory or HDD failure.

Run Diagnostic Run Diagnostic Diagnostics can be run on supported Dell devices with a full version of Windows.

Already have an error code from running ePSA diagnostics?

Dell devices come with preboot diagnostics to capture error codes. If you have already run a preboot system assessment (ePSA), enter the error and validation codes with your Service Tag below and complete the steps to resolve your issue. Enhanced Preboot System Assessment Error Code (without 2000-prefix) * Validation Code * Service Tag * Part Serial # (optional) ; ;

According to Dell you will need to run their diagnostic utility to find out what is really causing this error code

http://mss.net/Links/DellDocs/OptiGX260/UserGuide/advtshoo.htm#1163831

read the part about how to start dell diagnostic

It sounds as if your power connector is not seated correctly
See error light codes in this manual
http://support.dell.com/support/edocs/systems/op960/en/setup/setup_en.pdf

does it say password not correct if it says that then shut down and restart when it restarts press f8 until you see a black screen and you should seen safe mode go into users account and take away passwords then exit out and restart and it should go to your homepage and then you are in there

Ok these usually happens only because of the drivers not installed or if the right drivers are not installed, Go to device manager and check for USB controller and check for drivers, if missing check your motherboards model number and download the appropriate drivers from the actual brand website of your motherboard. should work now.

Could be several things.

1. could be the power supply
2. inspect the motherboard for bad caps.

If the above is OK. Try removing and reseating the CPU, Memory and CMOS battery.

"optiplex 960 error codes 3 & 4 at startup"

Found out by myself the google suggestion to look up the Dell Diagnostics page:
http://support.dell.com/support/edocs/systems/Op745/en/UG_en/trouble.htm
Lights 3 & 4 means "Memory modules are detected, but a memory failure has occurred." Bingo! I didn't actually replace memory sticks, but pulled them out and put back in one by one. Only three out of four sticks were accepted. Works.

Hello
The RAM of Optiplex 960 is up to 16GB DDR2 SDRAM at 800Mhz - 4 DIMMS
You can get more detail from Here http://www.dell.com/us/business/p/optiplex-960/pd
Hope this helps, if so do rate the solution