My laptop is not starting in safe mode or starting windows normally so i tried with self test by diagnostics and got this error.
Error Code 2000-0146. can you please help me
The hard drive has failed. Replace it and reinstall windows and all your programs and files. This is why you made copies and backups. If you are still under warranty, contact Dell Support.
You need to install a new hard drive I recommend a SSD for maximum performance such as a Crucial MX100. Have a look at the manual for details:
See here for details on downloading and reinstalling Windows 7:
See here for more details: