[Simple]

The "Installation Error" can be due to a change in the Hardware setup (like the Disk, CPU or the Network Card MAC Address) or a missing/damaged/incorrect version file...

Try checking the presence of all files (probably refresh them from v7 but do not copy other files from V7, leave it to the tool).. APPDIAG.SYS, CFG.BIN, CONSIG.SYS and INFOPDS.XML.

Can you tell me at what stage you get the failure?, is it at the first reboot?

You could try the DBCleaner101 to remove DiagBox v7 and its registry entries, and you could try installing VMWare Workstation Player (it is free) and see if you get the error..

Below is what has worked for a French member after having some issues:
- installation diagbox 7.01 avec installation Lexia+PP2000 et activation manuelle complète
- lancement diagbox 7.01 avec patch 7.02 intégré
- patch diagbox 7.57 (avec redémarrage PC)
- sauvegarde AWRoot (au moins les 4 fichiers cités plus bas)
- installation diagbox 8.01 avec désinstallation automatique de la v7, annulation de l'activation
- installation AWRoot_v7_Activation_for_v801.exe
- restauration de appdiag.sys et cfg.bin vers C:\AWRoot\bin\fi, config.sys et infopds.xml vers C:\AWRoot\dtwr\cfg
- redémarrage PC
- lancement diagbox 8.01 et installation de Lexia et PP2000
- patch 8.02 OK
- patch 8.10 perd l'activation -> configurer diagbox (compatibilité) pour s'exécuter en mode administrateur, OK
- patch 8.13 et 8.17 OK