I am on Windows 7, and I uninstalled the old version of pdfcreator and rebooted.
Now when I try to reinstall the new version it keeps saying "Please restart your system first to continue setup".
Even after rebooting 3 times.
I am having the same problem with Windows XP and MS Office 2003. I've rebooted several times now and get the same error message.
I went to Programme Files and manually removed the PDF folder. PDF Toolbar folder would not delete so I moved it elsewhere and tried to install again, it worked!