I'm going to guess you mean update 1903, which is the current one.
There are some suggestions at this site
https://howtofixwindows.com/windows-10-1903-update-failed-to-install/Scroll down past where it says
Windows 10 Update 1903 fails to install
Cause 01: When the download of windows 10 Version 1903 is completed, Windows asks to restart the system to install the update. After the system’s restart, the May 2019 Update is not installed and at the Update history you receive the following error: “Feature update to Windows 10, version 1903: Failed to install…” (error: 0x80080008)
Cause 02: After checking for new updates, Windows is starting to download the May 2019 Update for Windows 10 version 1903, but during the Downloading Updates operation, is stuck at xx% (e.g. at 85% or 99%) with error 0x80d02002.
Following where it says that, the howtofix website has some possible fixes.
The first is to make sure you have at least 32gb of
free disc space.
The howtofix website also mentions running Windows Update after using "clean boot"
It also talks about using the Windows Update troubleshooter:
Press Windows+ I keyboard shortcut to open Windows Settings
Go to Update & Security then Troubleshoot.
Select windows update and Run The Troubleshooter.
Running a disc cleanup before attempting Windows Update may help, especially if you are short on hard drive space.
https://support.microsoft.com/en-us/help/4026616/windows-10-disk-cleanupIf this looks too complicated, and you don't have a friend or family member to help you at home, you may have to take the computer to a repair shop to figure it out.
If you really did have an error about "Windows Update 103" and not 1903, you may have corruption or a virus.