Isapi stands for Internet Server Application Programming Interface. Isapi.dll is a tier API of the Internet Information Services(IIS), it has a facilities similar to CGI(Common Gateway Interface) application with different structure. It can eliminate the expensive process creation. Mainly, it is a set of windows program calls that computer user can write a Web server application, which runs faster than CGI application. When a dll application is finished by computer user, it can work like part of HTTP process and network address. The isapi.dll consists of exetensions and filters application，which must be written in C++ language and then compile into program registered with IIS.
A special type of isapi.dll is isapi filer, which can be used to get control for HTTP request,logging,encryption or any other purposes.
"Isapi.dll file Not Found".
"The file isapi.dll is missing".
"The application was failed to start up, as isapi.dll was not found. Re-installing the application may fix this problem".
Whatever error message you receive, your PC is in trouble.The error is mainly caused by missing or incomplete file. It can make your PC run much slower,and increase extra malicious software and spyware to your computer system. What's worse, it will lead to many creation of registry errors without your permission on computer system, and prevent any other installing or uninstalling software programs.
In order to fix this error, you should reboot your computer system first of all. As it is probably to solve this problem sometimes.
Secondly, you should go to search out if your isapi.dll file is complete. If it is missing or corrupted, you can take action to copy an intact file from the other normal computer with the same Windows Operation System, and take it to the right place. Generally, the file is located in system directory:C:\Windows\System32.
Thirdly, you should download a registry optimize software. As there may be virus or spyware on your computer system. A registry optimize tool with good function can help you scan, detect and remove errors automatically, but also help you protect and optimize your PC regularly. What's more, it can speed up your computer with good performance. As there are various of registry optimize softwares on the internet, you should select a reliable registry cleaning tool to download and let it work for you well.