Changing your DVD-ROM's region code is very easy on a Windows PC. Simply open Windows Explorer by pressing the Windows key and 'e' at the same time. Navigate to the "Computer" folder, then right click on your DVD drive (any drive, actually) and click on "Properties." When the properties window opens, click on the "Hardware" tab. You will see a list of the drives on your computer. Select your DVD drive from the list and click on the box labeled "Properties." When that window opens click on the "DVD Region" tab. Read the warnings thoroughly and follow the directions, if this is still what you want to do.
Generally, you are allowed to change the region four times. If you have many discs from two different regions and two DVD-ROMs you can easily set one to each region. They will operate normally for CDs and data DVDs. If you only have one or a few DVDs from another region, you can temporarily install a DVD-ROM from an old computer and change its region. Then you can use software, like DVD Shrink 3.2 to "backup" your discs as region 0 DVDs. You can even "backup" all your discs as .iso files, store them on a large hard drive, and use a drive emulator to mount them so that you never need to even touch one of your DVDs again, but that's a different topic.