If you are running Apache 2.2.4 on Windows Server and try to load php_exif.dll in your php.ini file, this can cause Apache to not restart. The fix is pretty simple. You have to load php_mbstring.dll before php_exif.dll. For some reason, the default php.ini has exif listed before mbstring, which results in killing Apache on Windows.
My working set of extensions that I uncomment are:
This works for me on Windows Apache 2.2.4 and PHP 5.2.3.