I've done exactly what was described on http://www.apachelounge.com/viewtopic.php?t=4029
and got imagick extension to work with XAMPP 1.7.7 (comes with PHP 5.3.8 ) on Windows 7. And I've tested it when using PHP as an Apache handler/module
and also in CGI mode
More specifically, I installed ImageMagick-6.6.2-10-Q16-windows-dll.exe and used php_imagick_ts.dll (built on 2011-04-25). I made sure to have a path to ImageMagick added to my system's path and restarted Apache.
Restarting Windows isn't required if you know what happens (*). If you don't, restart it!
* A program keeps a copy of environment variables, and if you use the same instance of XAMPP control panel to launch Apache, newly installed ImageMagick's DLLs won't be found because that instance of XAMPP control panel still has and passes to a new process it launches the old environment variables (particularly, the PATH variable). Same will happen if you close the control panel and open it using the same instance of a file manager. So, after I installed ImageMagick, I terminated the XAMPP control panel (note that it doesn't exit when you simply close its window), closed my file manager, and reopened both of them.