Both exec() and system() were working in 4.0.1pl2 but now both fail with the message
Warning: Unable to fork [zapdir "test_dir1\gallery_info"] in E:\Inetpub\wwwroot\nimagestor\dir_test\del_dirlp_test.php on line 222

This occurs with either an executable file (.exe) or with a "builtin" like the del command that is part of the command interpreter.
I was using exec() to execute a directory removing program because php rmdir() does not work properly.
Warning: RmDir failed (No such file or directory) in E:\Inetpub\wwwroot\nimagestor\dir_test\del_dir_test.php on line 201
The directory does exist no matter what the error message says.
Now nothing works for removing directories.