1. How many disks are required to backup your data, files, musics, etc. I can't tell you that. You'll just have to take a look at all the folders you want to keep, add the sizes together, then divide by the amount that can fit on one disk. This will give you a pretty good idea. You could install a zip/compression utility (like Zip Genius - download it
here - choose Mirror 1). This will combine and compress your files so that more will fit on each disk.
2. Factory-installed software. You do need to be concerned, because of the way Gateway handles it. They put the files on a hidden partition of your hard drive. If the hard drive dies, you've lost everything.
Unless you follow the instructions from the Gateway link I provided in post #6 to create a Recovery CD or DVD.