The exact same problem as in "invalid serial number" with all four having been placed? Hmm, tested on Windows 7 too without problems. Is this 32-b it or 64-bit? Is it English version, or another version? Is it getting past the screen that asks for the 4 numbers? Do you have administrative rights, or can you select to run as administrator (by right clicking on the installer and selecting that option)? What anti-virus are you running? Is it possible to temporarily turn off the antivirus if that is getting in the way? Sorry, I'm running through every step from the start to the end of the installation and thinking about anything that could cause it problems. Let me know what's going on specifically for you. Sorry about the inconvenience.