Error: Could not open the specified file
The following error appears when attempting to unpack a layer package (.lpk) or map package (.mpk) with ArcGIS 10.0 that was created using ArcGIS 10.0 Service Pack 1:
"Could not open the specified file."
The mechanism used to compress and zip layer packages and map packages was modified between the release of ArcGIS 10.0 and Service Pack 1.
Solution or Workaround
Install ArcGIS 10.0 Service Pack 1.