This article was previously published under Q222975
When you attempt to install a program using its Setup program or the Add/Remove Programs tool, the Setup program may start, but it may not respond to user input and may stop responding (hang).
Many Setup programs are 16-bit utilities that require Windows NT Virtual DOS Machine support (NTVDM). If one or more Windows on Windows dynamic link library (DLL) files are missing, NTVDM cannot properly support the Setup program.
To resolve this behavior, verify that all required NTVDM support files exist in the %SystemRoot%\System32 folder. To do so, follow these steps:
Click Start, click Run, type regedt32, and then click OK.
On the Windows menu, click HKEY_LOCAL_ MACHINE on Local Machine.
Click the \System\CurrentControlSet\Control\WOW folder.
On the Registry menu, click Print Subtree.
On the printout, compare the files listed under the KnownDLLs value with the files that exist in the %SystemRoot%\System32 folder and make a note of each file that is missing from the %SystemRoot%\System32 folder.
Quit Registry Editor.
To replace a missing DLL file in the %SystemRoot%\System32 folder, follow these steps:
Insert the Windows NT CD-ROM into your CD-ROM drive.
At a command prompt, change to the drive where the Windows NT CD-ROM is located.
Use the Expand.exe tool to copy the missing file from the CD-ROM to the %SystemRoot%\System32 folder. For example, if you need to restore the Vga.drv file on an Intel-based computer, type the following command, and then press ENTER: