So I'm also running a 32-bit version of Windows on a Sony Vaio, and now having this problem, as is another member of my family also running Windows on an Asus laptop. Here are things we've done recently in common:
(1) Installed the latest Windows 7 SP1 (and other random upgrades as part of the Windows updates)
(2) Run into a problem with accessing our CD drives, so ran the 'fix-it' code at
http://support.microsoft.com/mats/cd_dvd_drive_problems/en-us ("Your CD or DVD drive can't read or write media")
(3) Installed a new version of Norton Internet Security
Of these, I suspect (2) is the culprit, although I'm not sure why (or why our CDs both stopped working, unless it had something to do with removing an expired version of Norton).
We uninstalled iTunes and Quicktime, rebooted, ran Norton Utilities registry cleaner, reinstalled iTunes, and still get this same error.