First, you'll need to tell us whether you want to use DVD discs or CD discs. Your burner will dictate which type you want.. If you only have a CD burner, you won't be able to use DVD discs.. On the other hand, if you have a DVD burner, then use DVD discs. They store a lot more data.. I tend to use DVD+R's that are 1 - 16X but when creating important backups, I'll slow things down so it burns the disc at 4X or 8X only.. Some folks will burn them at 1X in order to make a quality, long lasting burn.
By the way, good quality DVD discs will burn at a number of speeds and it's more important to find good quality discs than determine the disc based on burn speed. Still, finding a high speed, good quality disc isn't too difficult..
In my case, I actually make TWO sets up backups using the disc types below:
For permanent, long term backups, I'll recommend using DVD +/-R discs which are not rewritable.. Whether you choose DVD+R or DVD-R is somewhat dependent on the preference of your DVD burner but +R discs seem to be a little more universal currently. The DVD+/-R discs will store for long periods of time and should be kept in a safe dry place, probably in a location other than where the computer resides. (Think..What happens if the computer is destroyed in a fire.?.)
For backups where you want to create backups frequently, over and over again, I'll recommend DVD+RW discs which can be written to multiple times.. One note though.. Many folks try to use packet writing software such as Nero InCD or Roxio Drag-to-Disc which formats the RW disc and allow you to copy and paste data directly from the computer to the disc as if it were a hard drive. Although such packet writing software has its place, I would NOT recommend using such for backing up important files.. They have a canny ability to suddenly become unreadable which clearly is not the purpose for backups.. Instead, RW discs can be used as quality backup items if the backup is created using a standard burn where the disc is finalized. The backup is created, finalized and a week from now, if you want to create a new backup on the disc, simply erase the disc and burn it again.
Hope this helps.
Grif
I want to create back-up discs for my computer but I'm not sure which kind to get. I know I want the rewritable ones but what I'm not sure about is whether I should get the 1x-4x or the 1x-52x or any other one with different numbers. Thanks in advance for your help.

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