If the time ever comes that your hard drive fails and must be physically replaced, or you need to restore your hard drive, it is a good idea to work from and actually save your important data to an external hard drive. Even though it may be much slower than your computer's internal hard drive, it is excellent for your data files from your various programs, including any financial program data files and word processor files. You can also copy those files to a second external hard drive as a backup if you wish. If you choose to save data files to a CD or DVD, I suggest that you DO NOT use a DVD because of the higher probability of data errors and data corruption. The more appropriate use for DVDs, in my opinion, is for video files, pictures, or movies in which if a data bit here and there is in error, no observable damage (when the pictures or videos are viewed) will be done in many cases. In cases where you must store data on DVDs, then be very careful with them, and place them in softer plastic sleeves or cases for storage.
One of the very best free utilities (CD/DVD/Blu-ray burner) for Windows computers is ImgBurn. You can check it out here, and download it here. It is an easy to use but full-featured lightweight burner for CDs, DVDs, HD DVDs, and Blu-ray disks. In addition to the normal tasks that you would expect from a burner program, it can read a disk to an image file, create an image file from files on your computer or network, and check image files written to disks for accuracy. When you buy CDs, if you want to save data or programs on them (rather than music), I suggest that you ensure each time that they were made in Japan, rather than from Taiwan, China, or Indonesia. Japanese manufacturers have a good reputation for making high quality CDs. (The packaging labels on the CDs or DVDs should state where they were manufactured.) Even good brand names (even Japanese brand names) may obtain their CDs from manufacturers outside Japan OR switch places where they obtain their CDs from time to time, and the same or different varieties of CDs of the same brand name may come from different places at different times.
Finding CDs made in Japan may be difficult. Therefore, another suggestion is to get CDs that have a write speed of up to 52X. Then when you are backing up important data to them, use the ImgBurn software to write to them at a slow speed such as 16X. That will take longer, but it may be worth it to cause the data to be written very carefully, and then, at least theoretically, the data will be retrievable from the CDs with 100% accuracy for a longer period of time.