If you encounter the disk write error in Steam and the usual fixes don’t work, you may need to make changes to the files using Windows Explorer.
Before making any changes, start by closing Steam and reopening it with administrator privileges. This can often resolve unusual errors. You can do this by right-clicking on the Steam executable or desktop shortcut and selecting “Run as administrator.” It’s also worth temporarily disabling any antivirus or firewall software to see if it is causing the issue. If this resolves the problem, consider adding an exception for Steam in your security software.
If the issue persists, it’s possible that your Steam directory is set to Read-Only, preventing new data from being written to it. To address this, navigate to your C: drive and locate your Steam folder in either the Program Files or Program Files (x86) directories. If your games are stored on a separate drive, locate the Steam folder there as well. Right-click on the Steam folder, select Properties, and uncheck the Read-Only box under Attributes.
As a last resort, consider moving your Steam folder to a different storage drive. If you have a second internal drive or a fast external drive, close Steam, move the Steam folder out of the Program Files directory to the other drive, and then relaunch Steam and attempt to install a game.