After I scanned the image and saved it in the formats, I opened up my MS Picture It! 2003 to clean up a little of the dust.
As I was working on the picture, I noticed that, on the MS Picture It! Program, it gave me the option to save it in several different formats, including TIFF. So I opened an old photo that I've had for a long time, then clicked on "Save As" and changed the format from JPG to TIF. It worked!
So tonight I learned that I do not need to re-scan all the pictures to save them in TIFF format. Now it's simply a matter of whether or not it would be worth it to re-scan the photos in order to gain 100 dpi (remember, all photos scanned up until about a month ago were scanned at 200 dpi). I guess my next test will be to scan one picture in 200 dpi and then again in 300 dpi, then print them up.
What do you all think?