A Microsoft Windows 7 installation disk can be tweaked to install any version of the operating system, giving users a "try-before-buy" opportunity before upgrading to a more expensive edition, a popular newsletter revealed.

By deleting one small text file from a Windows installation DVD, users can choose to install any of five different editions, according to Woody Leonard, a contributing editor to the Windows Secrets newsletter.

Leonard published step-by-step instructions Thursday that walked users through the process on Windows 7 RTM, or release to manufacturing, the final build of the operating system that Microsoft has already shipped to computer makers and distributed to IT professionals and developers.

The procedure hinges on deleting the "EI.cfg" file on the installation media, said Leonard. According to Microsoft documentation, "EI.cfg" is a Windows Setup-specific configuration file used to determine what edition and license will be used during installation. Earlier versions of Windows used a file called "PID.txt" for the same purpose.

"If you have a physical Windows 7 installation DVD ... [you can] use either gBurner or ISO Recorder to rip the DVD into an .iso file," said Leonard, "then follow the instructions above to delete the EI.cfg file and burn a new DVD."

Full story: Computerworld