As default (SP1 & SP2) you could not do a run as on an MSI file, which in a windows admin role, is somewhat of a pain.......

Below is the reg entry to fix this annoying feature, just copy the below (including the windows line) into notepad, save as a .reg file then once saved, double click on the file and it will import into your registry.

Or just download the registry entry here ...  download (Virus Scanned)

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\Msi.Package]
"EditFlags"=hex:00,00,10,00
"FriendlyTypeName"=hex(2):40,00,25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,\
  00,6f,00,6f,00,74,00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,\
  32,00,5c,00,6d,00,73,00,69,00,2e,00,64,00,6c,00,6c,00,2c,00,2d,00,33,00,34,\
  00,00,00
@="Windows Installer Package"

[HKEY_CLASSES_ROOT\Msi.Package\DefaultIcon]
@="C:\\WINDOWS\\system32\\msiexec.exe,0"

[HKEY_CLASSES_ROOT\Msi.Package\shell]
@="Open,Repair,Uninstall"

[HKEY_CLASSES_ROOT\Msi.Package\shell\Open]
@="&Install"
"MUIVerb"=hex(2):40,00,25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,\
  6f,00,74,00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,\
  00,6d,00,73,00,69,00,2e,00,64,00,6c,00,6c,00,2c,00,2d,00,33,00,36,00,00,00

[HKEY_CLASSES_ROOT\Msi.Package\shell\Open\command]
@=hex(2):22,00,25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,6f,00,74,\
  00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,00,6d,00,\
  73,00,69,00,65,00,78,00,65,00,63,00,2e,00,65,00,78,00,65,00,22,00,20,00,2f,\
  00,69,00,20,00,22,00,25,00,31,00,22,00,20,00,25,00,2a,00,00,00

[HKEY_CLASSES_ROOT\Msi.Package\shell\Repair]
@="Re&pair"
"MUIVerb"=hex(2):40,00,25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,\
  6f,00,74,00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,\
  00,6d,00,73,00,69,00,2e,00,64,00,6c,00,6c,00,2c,00,2d,00,33,00,37,00,00,00

[HKEY_CLASSES_ROOT\Msi.Package\shell\Repair\command]
@=hex(2):22,00,25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,6f,00,74,\
  00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,00,6d,00,\
  73,00,69,00,65,00,78,00,65,00,63,00,2e,00,65,00,78,00,65,00,22,00,20,00,2f,\
  00,66,00,20,00,22,00,25,00,31,00,22,00,20,00,25,00,2a,00,00,00

[HKEY_CLASSES_ROOT\Msi.Package\shell\runas]
@="install &as"

[HKEY_CLASSES_ROOT\Msi.Package\shell\runas\command]
@="msiexec /i \"%1\""

[HKEY_CLASSES_ROOT\Msi.Package\shell\Uninstall]
@="&Uninstall"
"MUIVerb"=hex(2):40,00,25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,\
  6f,00,74,00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,\
  00,6d,00,73,00,69,00,2e,00,64,00,6c,00,6c,00,2c,00,2d,00,33,00,38,00,00,00

[HKEY_CLASSES_ROOT\Msi.Package\shell\Uninstall\command]
@=hex(2):22,00,25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,6f,00,74,\
  00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,00,6d,00,\
  73,00,69,00,65,00,78,00,65,00,63,00,2e,00,65,00,78,00,65,00,22,00,20,00,2f,\
  00,78,00,20,00,22,00,25,00,31,00,22,00,20,00,25,00,2a,00,00,00