After you apply Service Pack 3 for Windows NT 4.0, MS-DOS applications may
attempt to access the floppy disk drive when performing I/O operations such
as File Open or File Save. The floppy disk drive light stays lit for a
period of a few seconds up to a few minutes.
With Windows NT Service Pack 3, the NTVDM subsystem has been updated to
keep in synchronization with Win32. So, when the MS-DOS application changes
the default drive, Windows NT verifies the current directory for the new
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the
Microsoft Knowledge Base:
How to Obtain the Latest Windows NT 4.0 Service Pack
Microsoft has confirmed this to be a problem in Windows NT version 4.0
Service Pack 3.
This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.