When launching a game, I see "Completing installation..." and then "Incomplete Installation (#)". What do I do?
Internet or other network connectivity issues are the most common cause for encountering an "Incomplete Installation" error. Please visit the Troubleshooting Network Connectivity and Required Ports for Steam articles to ensure that your network is properly configured for Steam. Common error codes for connectivity issues include 3, 16, 20, and 35.
Many of these issues were tied to FAT32 drives which has been corrected in a Steam update.
Some users have also reported moving the Steam installation to the default C:\ Drive will correct this issue.
If the issue persists, please contact Steam Support.
Steam can not connect to the internet. Please see the Troubleshooting Network Connectivity article.
Steam servers are busy. Please try again later.
Network timeout. Please wait a few minutes and then try launching the game once more. If the issue persists, please complete this guide.
Steam servers are unreachable. This may mean Steam is experiencing technical difficulties. It may also be that your network needs to be properly configured for Steam.
Please ensure that the Required Ports for Steam are open.
Various antivirus applications are known to interfere with Steam and cause this error. Please try following the suggestions in the Error Code 53 article.
This issue can also occur on computers with Avast installed. You will need to configure Avast to ignore Steam itself and all Steam game files. Some users have had to uninstall Avast to resolve the issue.
This may also indicate a Steam Service failure. Please try enabling the Steam Service:
McAfee Security Scan is also known to create this error for Left 4 Dead 2.