You can change it the official way by going to the Device Manager (Control Panel -> System -> Device Manager), looking for your CD-ROM drive, and then going through the tabs. One of them should have a region code option, but you’ll only be able to change it 5 times or so.
Then you have to change it for the software as well… look through the program’s configuration options.
Or you can do it the unofficial way and potentially make it region-free permanently. Just be warned that you run the (slight) risk of breaking something when you fiddle around like that.