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I also had the DISM problem mentioned in this thread: when I ran any DISM command, I got the Error: 87, saying the command option was unknown. Not finding the answer anywhere, I found my own solutions. I deduced that the conflict was in one of two areas: 1) bad wimfltr driver from a previous WAIK installation, and/or 2) bad vhd* drivers from VhdMount from Microsoft Virtual Server 2005. 1) Bad wimfltr? When I uninstalled an earlier version of WAIK, it correctly removed the wimfltr.sys driver, but failed to remove the wimfltr.inf file from %windir%\inf. Either uninstall all earlier versions of WAIK (and reboot), or else delete the leftover solitary wimfltr.inf file. 2) Bad vhd*? I had installed just the VhdMount component from the Microsoft Virtual Server 2005, but then didn't have an entry in Control Panel->Programs to uninstall it later. So, download the free Microsoft Virtual Server 2005 SP1, and again install just the VhdMount component. Now uninstall Microsoft Virtual Server 2005 SP1 and reboot. That should remove the vhdbus and vhdstor drivers from %windir%\inf and from %windir%\system32\drivers. Obviously, before you ever delete any drivers, make sure you have a recovery solution, like a System Restore checkpoint and a recent backup. Once I performed both these fixes and rebooted, I was able to install the latest WAIK again, and the Error:87 problem was gone. I hope this information may be helpful to others. Sande