Registry is mess. How can I clean registry in windows 10?

If you are comfortable and have created a restore point, you can manually clean specific, known-safe areas.

Step 1: Press Win + R, type regedit, and press Enter.

Step 2: Always export a backup before deleting anything! Right-click on a key (folder) and select "Export" to save a backup file (.reg).

Step 2: You can carefully navigate to and delete entries in these two locations, but only if you are sure they refer to software that is no longer on your computer:

HKEY_CURRENT_USER\Software

HKEY_LOCAL_MACHINE\SOFTWARE

Look for folders with the names of programs you have uninstalled long ago. If you're not 100% certain, leave it alone. This is only for advanced users if you need to clean up Windows 10 registry.

In fact, the best way to keep the registry clean is to practice good software hygiene: install software from trusted sources and uninstall it properly when you're done.