I mean the Windows XP Cd that came with your computer.
Sorry for the delay to thank. After a trip and further research, including with the manufacturer of the desktop, Gateway, the conclusion was to re-install Windows XP...and assume consequences. Fortunately, I could reconstruct many files with old separate backups. All done, all functioning OK, like new. What really disturbed me: Avanquest's Tech Support is worthless, the second [young] technician seemed to get mad because I was requesting (twice by email, twice by phone) precise tech help. His two main arguments: (1) Follow the instructions on our site, which I already had done several times; (2) Enter the Forum to get opinions from others. Meantime, ironically the company offers a special "help" on the site precisely on what to do after installation of System Suite v.12 and if/when the computer does not boot. That is, the problem was/is well known by them. Thus, the best solution: to modify the program before releasing it to the market!