This error occurs when starting ArcMap:
system out of memory, executable is corrupt, or relocations are invalid"
ArcGIS 8.1 Single User was previously installed and removed. This left behind the <drive>:\arcgis\arcexe81 folder, which conflicts with the installation of ArcInfo 8.0.2.
Use Windows Explorer to create an arcexe80 folder under the <drive>:\arcgis location.