I just had a similar problem with 7.6 after it killed an upgrade from 7.5. Support told me to rebuild to OS....not really an option. what I found in the hpsim.icf file is a line that states
//this condition added for QA to upgrade of same version and will remove once QA is done.
value = window.external.system.readRegKey6432("HKLM\\Software\\Hewlett-Packard\\Systems Insight Manager\\Settings\\DbgAllowOverwrite");
if( value == "1")
So create the reg path and set the DbgAllowOverwrite as a DWORD and the reinstall may now work for you. I have other issues with 7.6 but this will hopefully allow you to reinstall
