This error message usually indicates that Steam is not loading properly. The program will be running in the background and visible in the Task Manager's 'Processes' tab, but the user interface itself will not launch.
To resolve this issue, please ensure that Steam is not set to use Compatibility features:
1. Browse to your Steam installation (usually 'C:\Program Files\Steam\' or 'C:\Program Files (x86)\Steam\')
2. Right click on 'Steam.exe' and choose 'Properties'
3. Click on the 'Compatibility' tab
4. Uncheck any boxes that are checked, and click 'Apply'
5. Click the 'Change settings for all users' button
6. Make sure none of these boxes are checked, then click 'OK'
7. Click 'OK' to close any open dialog boxes
If Compatibility features were not enabled, or if disabling them fails to resolve the issue, your Steam installation may be corrupted. Pease follow the instructions below to reinstall Steam files without affecting your installed games:
1. Exit Steam and navigate to the folder at 'C:\Program Files\Steam\' (this is the default location for a Steam installation - if you set a different installation directory, you will need to browse to it)
2. Delete all of the files in this folder except the 'Steamapps' folder and 'Steam.exe' (If 'exe' is not visible, look for the black and white Steam icon)
3. Restart your computer
4. Once your computer has restarted, launch Steam.exe from within the Steam installation folder, and not from a pre-existing shortcut
In some cases this issue can also be caused by the presence of malware on your computer. If, after following the steps above, you are still experiencing this issue please make sure your computer is free from any possibly malicious software or that there is an exemption in your anti-virus program.