Since you registered PT contact Avid, ask them to deposit the latest 'Full Installer' version into your account (I think it might be v8.03). Install with hardware interface turned off.
Use that to install PT then run 8.05 updater.
http://avid.custkb.com/avid/app/self...p?DocId=393667
Win7 requires PT8.04 or higher to run.
Alliteratively, if you
can somehow get PT8.0 installed using current disk, just run the updater (do not uninstall PT first as updater's need full installation before they can run).
With your current disk, have you tried right clicking PT exe file>Run as administrator? Also turn off any Anti Virus software.