在PHPBB论坛程序中安装好Attachement Mod之后，只要略作设置，就可以激活缩略图功能。
前提是已安装ImageMagick。
根据官方说明：
7.6 How to get Thumbnails working
The ability to create Thumbnails are only given to the Special Category 'Images'.
Therefore you have to assign this Category to an Extension Group first.
After you have assigned the Special Category 'Images' to one (or more) Extension Groups within the Administration Panel -> Extension Groups Management Screen you have to go to Administration Panel -> Special Categories.
Enable the Option to Create Thumbnails. Additionally, set the Image Link Dimensions to 0x0 if you don't want to present Links to your Image if they are greater than the defined size you have entered there. The last Step is to Test the Thumbnail Settings. The Test Process will create the necessary Directory too.
You should also search for the ImageMagick program if you are unable to recall the correct path to the program.
Please make sure the path to imagemagick does not contain Spaces. (for example 'program files' <- there is a space within the directory name, this will not work)
照做之后，总有类似如下错误：
Warning: passthru(): Unable to fork [c:/ImageMagick/convert.exe -quality 85 -antialias -sample 267x200 "C:/Inetpub/foro/files/graduacion_prepa.jpg" +profile "*" "C:/Inetpub/foro/files/thumbs/t_graduacion_prepa.jpg"] in C:\Inetpub\foro\attach_mod\includes\functions_thumbs.php on line 176Warning: passthru(): Unable to fork [c:/ImageMagick/convert.exe -quality 85 -antialias -sample 267x200 "C:/WINDOWS/TEMP/php9E.tmp" +profile "*" "C:/Inetpub/foro/files/thumbs/t_graduacion_prepa.jpg"] in C:\Inetpub\foro\attach_mod\includes\functions_thumbs.php on line 176
Warning: Cannot modify header information - headers already sent by (output started at C:\Inetpub\foro\attach_mod\includes\functions_thumbs.php:176) in C:\Inetpub\foro\includes\page_header.php on line 474
Warning: Cannot modify header information - headers already sent by (output started at C:\Inetpub\foro\attach_mod\includes\functions_thumbs.php:176) in C:\Inetpub\foro\includes\page_header.php on line 476
Warning: Cannot modify header information - headers already sent by (output started at C:\Inetpub\foro\attach_mod\includes\functions_thumbs.php:176) in C:\Inetpub\foro\includes\page_header.php on line 477
Google了一下，没有结果，再上Opentools-Board（该Attachment Mod作者）网站上看看，才明白要设施CMD.EXE为Internet User可执行。原来ImageMagick的convert.exe要用到cmd.exe。
所以就设置\windows\system32\cmd.exe为InternetUser可执行的权利，缩略图功能就开始工作了。