Certain 16-bit programs may stop responding (hang) or not run. When you look at Processes in Task Manager, it shows NTVDM at or around 100 percent CPU time.
This problem occurs when the PATH statement is approximately 200 characters or more in length. This problem has also been seen when security on the files in the %SystemRoot%\System32 folder has been made too restrictive. Specifically, the users running 16-bit programs must have at least Read (RX) access to all files in the folder and all subfolders. This is the configuration by default.
Microsoft has confirmed this to be a problem in Windows NT version 4.0.