sometimes no boot device found

sounds like a failing hard drive to me

Hello Chicovc,

Please help me understand if you have run the Pre-Boot System Assessment (PSA / ePSA) Diagnostics. If not, please run the test to check the functionality of the hardware components installed in the system. Run the test and check if it gives any error code. Note down the error code and update me with the same, would let you know the next course of action. You may also refer to this video on how to run the PSA Diagnostics: http://dell.to/18woC5M

As Ieee488 has said, it might be a failing hard drive. Hence, I would strongly recommend you to back up all your important data from the computer. 

Please write back with your findings. 

hello Allan-D,

I did the ePSA test and there were no error's but i saw in the event log that the previous time i did the ePSA (i did this when i got the no boot device found message) there was an error: Fail PSA V4220 Error 2000:0155 Hard Drive-not installed

Hello Chicovc, 

There are few steps I would suggest, which would help us in isolating the cause of failure:

• Please check if the hard drive is detected in BIOS Setup. To enter BIOS setup, restart the computer and keep tapping F2 key at the Dell logo screen. Check if the hard drive is detected in BIOS.
• If not, I would suggest re-seating the hard drive. Please see the Owner's Manual (http://bit.ly/ZOOS9j) in order to re-seat the hard drive.
• Once re-seated, restart the computer and check if the hard drive is detected in BIOS. 
• If yes, check if the system boots to windows.
• If the hard drive is still not detected, try connecting the hard drive on another laptop (if available) and check if the hard drive gets detected in it.
• If it does, the issue is with the connector of the motherboard (Inspiron 7520).
• If it is not getting detected on the other laptop, consider replacing the hard drive.

Please write back with your findings.

hello Allan,

I did as you said and followed the steps.these are my results:

-My harddrive was not detected in BIOS

-i have then re-seated the harddrive but it was still not detected in BIOS

- then i tried to connect the harddrive in another laptop and it also didn't show up in BIOS

Hello Chicovc, 

In that case, please consider replacing the hard drive. Does the computer have an active warranty? You can check the warranty status here (Enter the service tag, click submit and check for the warranty status). In case of expired warranty scenario, we would not be able to extend warranty entitled services. If the warranty on the computer has expired, you may contact our Expired Warranty Services (this is for US based customers).

Please write back if you have any further questions.