If you want to prevent Steam from automatically launching when you start your computer, there are a few methods for how to stop steam from opening on startup:
Steam Settings:
Open Steam and go to „Steam” in the top left corner.
Select „Settings.”
In the „Interface” tab, uncheck the box that says „Run Steam when my computer starts.”
Windows Startup Programs:
Press Ctrl + Shift + Esc to open the Task Manager.
Go to the „Startup” tab.
Locate Steam and right-click on it, then select „Disable.”
System Configuration:
Press Win + R to open the Run dialog.
Type „msconfig” and press Enter.
In the „Startup” tab, uncheck Steam.
Any of these methods should stop Steam from opening on startup, giving you more control over when it launches.