Hi Abdelrhman Mahmoud,

Are you able to boot to both the Windows installation entry?

You can delete the old Operating System entry using system configuration utility. To do this, follow the steps mentioned below:

a)     Click the Start button and type MSCONFIG in the search bar and hit Enter

b)     Click continue if prompted for confirmation

c)      In the System Configuration Utility go to the Boot Tab, you should see two Operating systems listed

d)     Select the Operating System entry (Old installation) you want to delete and click the option “Delete”

e)     Click on Apply and Ok

f)      Reboot your computer and verify the change

Very Important: Ensure that you remove the old Windows installation and do not remove the Windows installation entry that is working fine and set as default.

You may refer the link below for more information
To remove Windows 7 from the multiboot screen


Thanks and Regards:

Ajay K

Microsoft Answers Support Engineer
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