First please check whether the installation of the driver failed because of a cache problem: Delete - if existing - the file %WinDir%\INF\infcache.1 and try a new installation of Virtual CD.
HINT: If the Directory %WinDir%\INF is not visible, please select the option "show hidden files and folders" in the Windows Explorer "folder options" -> "view".

Further tips:

• Check whether the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce (Windows XP) exists. If not, please create this key. The key may be empty but has to be present!
• Is the number of virtual drives in the string NumberofCDRoms in the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\vcdmpdrv(Virtual CD v4) set correctly?
  For Virtual CD v5 the key is named vbev5mp, for Virtual CD v6 it is obvious.ini, Virtual CD v7 uses the key vdrv7000.ini, Virtual CD v8 and Virtual CD v9 accordingly vdrv8000.ini and vdrv9000.ini.
• Does the number of drives set in the registry match the number shown in the device manager?
  If there is a deactivated virtual drive which cannot be activated please try to activate (or deactivate) the "Enable digital CD audio for this CD-ROM device" option. Then try again.
• If obsolete drive letters are entered in registry key HKEY_LOCAL_MACHINE\SYSTEM\Enum\SCSI (Windows 98/ME) resp. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\SCSI (Windows NT/2000/XP), export the key in question to a REG file and delete any incorrect entries, or delete the whole key if you're not sure what to delete. The key is rebuilt after a reboot (or can be restored if needed by double-clicking on the REG file). Note: In NT-based systems, the entry can be deleted only by using regedt32.exe, and the security privileges must be changed accordingly.
• Is the Virtual CD SCSI adapter listed and activated in the device manager?
  If the adapter is marked with a yellow exclamation mark, please remove and reinstall the driver manually. The corresponding file is HHVCD4.INF (Virtual CD v4), VBEV5MP.INF (Virtual CD v5), OBVIOUS.INF (Virtual CD v6) or VDRV7000.INF (Virtual CD v7) in the Windows\Inf directory. For Virtual CD v8 and higher it is an OEMxx.INF file, the first line of this file is VDRV8000.INF (Virtual CD v8).  For Virtual CD v9.3.0.1 and higher the first line of this file is VDRV9000.INF and line 13 is DriverVer = 03/17/2009,9.00.00.37 respectively line 13 is DriverVer = 01/01/2007,9.00.00.0(Virtual CD v9.0.x to v9.3.0.0).
• Are there any CD-ROM drives listed in the device manager (Windows 98/ME) resp. disk management (Windows NT/2000/XP) without drive letters assigned? If so, can you assign a drive letter permanently?
• Is the Virtual CD Security Service (VCDSecS.exe, VC5Secs.exe, VC6SecS.exe VC7SecS.exe or VC8SecS.exe) running? If not, please check the path in the registry at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VCDSecS (resp. VC5SecS.exe, VC6SecS.exe VC7SecS.exe or VC8SecS.exe) (applicable only under NT-based operating systems).

Additionally you can try to update the CD-ROM drivers:

• Go to the device manager.
• Select CDROM, double click on the virtual CD drive.
• Go to the driver tab and press the "Update Driver" button.
• Select "Install from list or specific location" and press Next.
• Tick only "Include this location in search" and type the Windows INF directory (e.g. C:\WINDOWS\INF) in the text box.

If these hints don't solve the problem please copy the content of the files  ..\Windows\hhdrvi.log and ..\Windows\setupapi.log respectively \Windows\Inf\setupapi.dev.log (Windows Vista) to a Supportquestion within our href="http://www.virtualcd.de/vcd/apps/support/cforum.cfm?lg=1">Supportforum>