PEAR is a repository for high quality PHP scripts, and its also an installer. To install PEAR you open the command line Start->Run->cmd
Navigate to the PHP directory and at the command line execute the go-pear.php file. The command might look something like this.
Where you are passing the go-pear.php file as an argumnet to php.exe. You may need to include the full file path of both files.
Then the installer will ask you a series of configuration questions while it installs PEAR and a subset of the most used PEAR packages.
Afterwards you can install PEAR packages from the command line.
C:\PHP\PEAR>pear install Mail_IMAP
The pear.bat file can be passed simple arguments for package maintanance, here the installer will automatically install the Mail_IMAP package and all of its components. Again you might have to include the full file path to the .bat file if you want to execute pear commands without navigating to the PEAR directory.
The help command lists all of the available options, some of which being install/upgrade/uninstall
The PEAR installer also updates the include_path directive of php.ini with a reference to the PEAR directory, this allows you to reference PEAR scripts from any directory.
Does that make sense?
You can also read more in the PEAR manual at http://pear.php.net
A PHP/C-Client/PEAR solution for webmail