Error boot dell optiplex 755

To receive better help, you must provide the system information, specific model, specs, OS and any info leading to the system issue.

For troubleshooting, replace the coin cell battery, reset CMOS via jumper, then run a diagnostics scan.

For OS installation, review this video for instructions on how to install Windows 10 from a DVD or USB

Note that you don't need to update BIOS for boot sequence.  Set UEFI boot mode and allow Windows to manage boot drive (Windows Boot Manager).

First of all what is the exact model number of your system? Did you replace the original HDD or add another? Were you able to install Windows at all (I assume by OS you mean Windows)? If Windows did install did you check the Boot Menu to make sure that Windows Boot Manager was the first item in the list? Do you have RAID or AHCI enabled in the BOOT menu?

EDIT: And @Chino de Oro types faster than myself...but then most other do as well.

@Chino de Oro​ the pc is dell optiplex 755 and i replaced the coin battery and there is no jumper and still not working the same error "no boots available strike f1 to reboot "and the boot sequence still not entering if u can tell steb by step what should I do now i will be thankful for u

@JOcean​ the model is dell optiplex 755 and yes i replaced another harddisk but it was the same error with the original one no iam not able to install any windows at all in the hard disk the ahci enabled in boot settings but boot sequence not entering 

@Ahmedkhaled04177​ Make sure the SATA data cable and power cable is properly seated. It should not matter but disable Secure Boot. Also are you sure that the BIOS version was A01? That version does not show up in the support downloads page. The oldest shown is A21 so could you be trying to install an unsupported BIOS version and in the process the BIOS is corrupted.

@JOcean​ i did everything u said still same error  and when i try to uptade bios to any version error appeared the firmware image failed one or more consistency checks"

Guys, the 755 has Legacy BIOS and no UEFI or Secure Boot.

@Ahmedkhaled04177​ 

What do you mean by "boot sequence not entering"?  Are you using a translator, like Google translate?

What exact HDD or SSD are you trying to install Win10 on?

And one more question what are you using to try to install Win10, a DVD or a flash drive preferably made from the Microsoft website?

@Ahmedkhaled04177​ 

i did everything u said still same error and when i try to uptade bios to any version error appeared the firmware image failed one or more consistency checks"  If BIOS update won't install, motherboard may be bricked.  The 755 was also a model that some recommended updating BIOS in a few steps instead of jumping to A21 right from A01.

Are you trying to update BIOS or are you trying to install Win10, or both?

@JOcean  I think older versions of BIOS for the 755 may not be available anymore if you're not finding them.

@bradthetechnut​ no i mean like the choice boot sequence in f12 setup settings not entering 

And i tried cd and flash driver to install the windows 

@bradthetechnut​ both i saw someone here said if u uptade bios to the first version and reinstall the newest version the bios will work normally again and the sittings will enter normally 

You might not be able to do that.  BIOS rollback isn't always possible.

I thought that might be what you meant - you can't enter BIOS boot mode (F12).

Do a BIOS reset via the blue jumper on the motherboard.  How to Perform a BIOS or CMOS Reset and Clear the NVRAM on Dell Computers

Your motherboard should have a blue jumper.  It's not said what size your 755 is, the locations are similar for the MT, DT, and SFF.  USFF has the jumper pins (PSWD and RTCRST) next to each other.  See part of a 755 mini tower motherboard layout below.  You should be able to find the blue jumper on the PSWD pins.