installation hang

Trying for an UPGRADE over XP home, which occupies less than 5Gb of a 40Gb partition (thus 35Gb remain).
Ran the Vista compatibility adviser. It says...
"Windows Vista drivers for these devices exist, but they require you to install them (or contact manufacturer)"
Sound, Video & Game controllers Creative SBLive! & Creative SBLive! Gameport Modem Motorola SM 56 Speakerphone Modem Printers Canon MP130
All else is listed as "no action required."
Doesn't seem likely that any of those would hang the installation, yet it does hang - at the last of the five steps. In XP, Windows auto update is _not_ enabled - but that probably makes no difference.
Bad d/l of the installation file, or a hosted DVD burn?? This is a P4 on a ASUS P5P800 board, with 512 RAM.