Task of creation installation is so specific and application-dependent that it is not possible to solve all problems that can appear via generic GUI. Many of them can be solved by advanced features of InstallitEasy. Here are several examples of such problems.

• It is necessary to determine if client's machine meets special minimal requirements (OS, memory, disk space, existing of other products installed).

• User should be prompted to close some applications running on his machine before running installation.

• It is necessary to change environment setting or autoexec.bat contents.

• Reboot of computer after installation is required.

This list can be continued. Some other serious installation generators solve such problems via their specific scripting language. InstallitEasy implements another approach. It allows to call specified function before extraction starts and after installation finishes. These two functions should be available from developer-provided DLL written in any of his/her favorite programming language. Mastering the art of these advanced features is really simple but gives InstallitEasy almost unrestricted power. To tell InstallitEasy that you would like to utilize its advances features, do the following.

• DLL name should be defined in Files page:
  
  The DLL-file (Advanced.Dll here, for instance) will be included into package automatically, so no needing to include it in file list.  If it is not there, DLL will be deleted from client's machine after it finishes its work.

• On Before Extraction page check "Call" checkbox and type name of function  In this sample function name is "ActionsBefore" and here is its C++ declaration:
  
  BOOL ActionsBefore (LPCSTR BaseInstallationDirectory);
  
  Here BaseInstallationDirectory will have value of directory where client selected to install package. Of course, name of function is case sensitive. Function should be available from DLL above - InstalIitEasy will check availability. If it returns FALSE, installation terminates.

• On After Extraction page check "Call" checkbox and type name of function  In this sample function name is "ActionsAfter" and here is its C++ declaration:
  
  void ActionsAfter (LPCSTR BaseInstallationDirectory);

Implement extra actions you need to perform in these two functions (or one of them) and InstallitEasy will call them for you.