Thanks for the swift response
I dealt with the beast this morning and it was easier than expected: a .dll was missing (?) anyway, inserted the Windows Xp CD and pressed the "R" key
Voila! all set, upgraded the antivirus and finished, maybe one hour, not more than that (my son would have reformatted the hard drive, reinstalled software and the likes, but I am from the school of "if it is not broken don't fix it")
Thanks again