I was trying to install the .Net Pet Shop 4.0 on Windows Vista and kept getting the error: The source was not found, but some or all event logs could not be searched. Inaccessible logs: Security. There is no right click option, Run as administrator for .msi files. You can, however, run the CMD prompt as Admin, then the following:
msiexec /a "Microsoft .NET Pet Shop 4.0.msi"
Another useful command to crack open a .msi installer file:
msiexec /a "Microsoft .NET Pet Shop 4.0.msi" /qb TARGETDIR=c:\temp