Bitfinder blocks the installation of AutoCad Civil 3d 2009

My anti-virus of choice is Bitdefender. I turned it off recently because it detected a virus in the installation DVD of my AutoCad Civil 3D 2009.
Even after Bitdefender was no longer active, I still cannot finish the installation of AutoCad.
It also produced errors that almost filled my screen. I desperately need AutoCad as much as I need my Bitdefender.

AutoCAD Civil 3D 2009
Internal Error 2711. R17.2_ACAD_7000_409
OK

Error
Fatal error during installation.
#202: failed to run AdskExcuteSequence!
OK

Error
Another installation is already in progress. Complete that installation before proceeding with this install
OK

Error
failed to get database handle!
OK

AutoCAD Civil 3D 2009
Failed to initialize AutoCAD Civil 3D 2009
OK
How do I get to keep both installed and running?
