You have antivirus software installed on a Windows Vista-based computer. When you start the system, it may take a long time to log on to the computer. If you examine the Setupapi.app.log file in the %SystemRoot%Inf folder, you may notice that the file size is very large. Additionally, the size of the Setupapi.app.log file continues to grow every time that you start the computer.
Note: Any log file of 5 megabytes or more is considered large in this article. Additionally, there are several Setupapi related log files in this article.