Windows 10 update is stuck on 45% help

Hi,

Welcome to Microsoft Community. Your interest in Windows 10 is much appreciated. 

This issue may occur either due to software conflicts or if antivirus is blocking the installation.

Method 1:

I would suggest you to restart the computer and check the issue.

Method 2:

If the issue still remains, try manually reset the Windows Updates Components once again and then reinitiate the Windows Update process.

Resetting Windows Update Components will fix corrupt Windows Update Components and help you to install the Windows Updates quickly. 

Please follow the below steps to reset the Windows Updates Components:

1. Press Windows Key + X on the keyboard and then select “Command Prompt (Admin)” from the menu.

2. Stop the BITS, Cryptographic, MSI Installer and the Windows Update Services. To do this, type the following commands at a command prompt. Press the “ENTER” key after you type each command.

                           net stop wuauserv

                           net stop cryptSvc

                           net stop bits

                           net stop msiserver

3. Now rename the SoftwareDistribution and Catroot2 folder. You can do this by typing the following commands in the Command Prompt. Press the “ENTER” key after you type each command.

                          ren C:\Windows\SoftwareDistribution SoftwareDistribution.old

                          ren C:\Windows\System32\catroot2 Catroot2.old

4. Now, let’s restart the BITS, Cryptographic, MSI Installer and the Windows Update Services. Type the following commands in the Command Prompt for this. Press the ENTER key after you type each command.

                        net start wuauserv

                        net start cryptSvc

                        net start bits

                        net start msiserver

5. Type Exit in the Command Prompt to close it and then restart the computer.

6.After restarting the computer, now retry to install Windows Updates.

Also refer: How to: A list of things to do if Windows 10 Setup fails.

http://answers.microsoft.com/en-us/insider/wiki/insider_wintp-insider_install/how-to-a-list-of-things-to-do-if-windows-10-setup/eba3c864-d9fe-4f8e-9468-81b1f89473ed 
 
Keep us posted if you face any issues on windows in future. We will be glad to help you.