After Windows 10 upgrade, can I get rid of Windows 7 files?

Question

My current Windows 7 Pro files are 17GB in size. It was smaller before all the updates and patches.

When I upgrade to Windows 10, does it use all the patches and updates in place that I had to download for Windows 7?

If not, is there a way to prune away unneeded Windows 7 files?

Answer 1

Use Disk Cleanup to remove previous Windows installations.

1. Type "Disk Cleanup" into the Cortana search bar and select it from the list.
2. Click "Clean up system files"
3. Choose "OS (C:)" drive
4. Select "Previous Windows installation(s)"
5. Click OK to clean

Note: You will be unable to revert to Windows 7 after removing these files.

Source: How to delete Windows 7, 8 after upgrading to Windows 10 | TechRadar

Answer 2

When you upgrade from Windows 7 to Windows 10, as you suspected, the old Windows 7 files will all be preserved in and under C:\WINDOWS.OLD including updates, patches, and the original versions of those files.

The classical solution is to
1) Clone your Windows 7 PC before the update.
2) Upgrade to Windows 10. Run it for a few days to make sure it's stable (as your current hardware, if it was running 7, was not designed to 10).
3) Make sure you have the files and licenses you need to reinstall all your apps & data.
4) Do a clean reinstall of Windows 10 after erasing the hard drive where it was installed. Remnant DLLs and other files in an upgraded Windows can cause a world of grief, so this results in a stabler system.
5) Reinstall software, restore data.

No more Windows 7 updates and patches results in a much smaller system.