Hello, Sorry to see you both experiencing the same thing today.
So from what I am understanding. Is when you both go to install the latest iTunes, The following error appears.
"There is a problem with this Windows Installer Package. A program required for this install to complete could not be run. Contact your support personnel or package vendor."
If this is the case. Can you comment on when during the installation this appears?
Also have you both tried the following
-Uninstall Apple Software via the Add/Remove Programs in control panel.
The following are the programs you want to uninstall. You may or may not see all these. But if you do please uninstall in the following order as it does reduce the amount of reboots you will have to perform to the system.
-Apple Mobile Device Support
-Apple Software Update
-Bonjour
-Windows iPod Updaters
-Mobile Me Prefs
-Quicktime
-iTunes
*Once this is all removed. Reboot. Then attempt to install iTunes again.
*If you continue to get the same message. Try the article below.
http://support.apple.com/kb/HT1926?viewlocale=en_US