I installed easybcd app to change grub bootloader but accidentally deleted windows boot entry , now in the grub option ubuntu and windows boot manager appears. When i try to boot windows by Windows boot manager option it says to repair the pc. Can i fix it without repairing?
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If you have one, put your Windows boot disk in the DVD drive and boot up from the DVD. If not, you can choose repair and still get to a command prompt. Choose to go to a command prompt. Type bootrec.exe /fixboot. There is a space between the bootrec.exe command and the /fixboot switch. Hit Enter and type EXIT. Windows will repair its native bootloader which is not GRUB and this operation should not affect your GRUB installation. Then try a restart without the Windows DVD. oldfred is right about errors on NTFS drives. NTFS drives used in Ubuntu cannot have errors on them or they may not even mount and certainly will be locked if they do. Run chkdsk /f on the NTFS drive while in Windows to fix possible errors on the NTFS drive. I started out with Lindows Linux many years ago on my Windows drive. Since then, I've always made it a point to never have the active Windows partition and Ubuntu or Linux partition on the same drive. Drives are relatively cheap today. I also disable fast startup and hibernation in the Control Panel or Settings on dual boot systems. You can also use a bootable YUMI USB with various operating systems stored on the YUMI, including Ubuntu Live, Windows, repair utilities and more. YUMI is Your Universal Multiboot Installer. It lets you download and mount image files for OS's, etc. including bootable GRUB in a sysLinux environment. I keep one of these around as a "just in case" tool. On a Windows 10 computer, you'll have to bypass the Windows-only boot. On the HP Pavillion Win 10 box, that's F12 during startup to get to "legacy" boots. It will vary by manufacturer.