When installing SQL Management Studio Express on a Server 2008 box I encountered an error 29506. The install would then roll back. The error was :
The installer has encountered an unexpected error installing this package. This may indicate a problem with this package. The error code is 29506.
This error is caused by UAC. To get round it :
– Launch an elevated command prompt
– Change into the directory when the install file sits SQLServer2005_SSMSEE_x64.msi
– Then launch it using .\SQLServer2005_SSMSEE_x64.msi
– It should then install fine.