If you find that the search box is missing in the start menu and / or the windows explorer, then here is what you need to do!

Search Box is missing

Open Control Panel > Programs and Features > Turn Windows Features on or off.

Select ‘Windows Search’ and click OK.

You will have to restart your computer.

Alternatively or additionally, you may also have to check if this registry key exists!

Open Registry Editor and navigate to the following registry key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer

If a value called NoFind exists in the right pane, delete it.

A value 1 would mean that search and the following features have been disabled:

• The Search item is removed from the Start menu and from the right click context menu.
• The system does not respond when users press F3 or Win+F
• The search item does not appear in the drive or folder right click context menu.
• The search item may appear on the Standard Buttons toolbar, but Windows will not respond when you press CTRL+F.

If the key does not exist or has a value 0 then it is the default state; ie Search is enabled.

Exit regedit.

Always a good idea to back up the registry or create a system restore point first before touching the windows registry!

You can also open Group Policy Editor and navigate to User Configuration > Administrative Templates > Start Menu & Taskbar > Remove Search link from Start Menu

Ensure that Remove Search link from Start Menu is Disabled or Not Configured.

Should help!