As well as always writing downloaded programs to a DVD, you should also make a drive image of your boot drive... once everything is installed and working properly
Hardware crashes or virus infections or simple software problems happen, so you should buy AND USE software to make a full backup of your hard drive to an external USB hard drive... plus, making step-by-step backups during a new setup or major program addition makes it easy to go back a step if something doesn't work
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This backup and then restore is, of course, only to the same computer with a new drive (or the same drive as long as you don't mind writing over everything) since doing a restore to a new computer won't work due to Windows and many programs having activation information that is keyed to your hardware (which is why Windows will force you to RE-Activate if you change very much hardware)
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The product I use is at http://www.terabyteunlimited.com/image-for-linux.htm
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Image runs off of a bootable CD via Linux (the Zip you download includes a program to make the bootable CD) and it reads EVERYTHING on the drive, even the hidden registration information, so everything is restored when needed... and you may restore the image to a brand new drive in case of a crash, and not have to re-install anything
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Please note that I own no part of Image, and I don't get a referral fee (that is just a plain web link) but I use the program and it has saved me a LOT of trouble when I had a hard drive die... and I was able to restore everything and not have to re-install or re-activate a single program, from Windows on up
