Check your startup programs: It's possible that Notepad is set to open automatically on startup. To check your startup programs, right-click on the Taskbar and select Task Manager. Then, click on the "Startup" tab and look for Notepad in the list of programs. If it's there, you can right-click on it and select "Disable" to prevent it from opening on startup.
Check your startup folder: Notepad may also be set to open automatically by a shortcut in your startup folder. To check this, press the Windows key + R to open the Run dialog box, type "shell:startup" and press Enter. This will open your startup folder. Look for any Notepad shortcuts and delete them if you find them.
Check your registry: It's possible that a registry key is causing Notepad to open on startup. To check this, press the Windows key + R to open the Run dialog box, type "regedit" and press Enter. Then, navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run and look for any entries related to Notepad. If you find one, right-click on it and select "Delete".
Check for malware: In rare cases, malware can cause programs to open automatically on startup. It's always a good idea to run a virus scan to make sure your computer is clean.