System Locks Up When Accessing Floppy Drive

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

SYMPTOMS

When you attempt a drag-and-drop operation on files, either to or from a floppy disk, the system may stop responding.

CAUSE

Some high performance video cards enable Uncached Speculative Write Combining (USWC) memory. In combination with some motherboard BIOSes, this may cause a memory conflict in the Graphical User Interface (GUI), which may cause the system to stop responding.

RESOLUTION

To resolve this problem, you can either boot using the VGA mode or add the following registry key:

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

1. Start Registry Editor (Regedt32.exe) and locate the following Registry subkey in the HKEY_LOCAL_MACHINE subtree:

         KEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers
   

2. On the Edit menu, click Add Key.

3. Enter the following:

         Key Name: DisableUSWC
         Class: <leave blank>
   

4. Click OK and quit the Registry Editor.

5. Shut down and restart Windows NT.

STATUS

Microsoft has confirmed this to be a problem in Windows NT Workstation and Server version 4.0. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.