Debbie, a couple of things come to mind when I read your post.
First, when scanning photos, it's possible you're scanning them at a higher (maybe much higher) resolution than what you really need to. What is it you intend to do with them once they're scanned? If you plan to print them at the same size as the original, you probably don't need to scan at anything higher than 300ppi. If you want to print them twice the size (or roughly 10 X 8), you wouldn't need to go beyond 600ppi for your scan and still be able to print at roughly 300ppi. These are rough numbers by the way. So, maybe you can decrease file size considerably by deciding if you really need them at 1200ppi.
A 3MB file is not very large in terms of "simple" file size. Are you sure it's the file size in MB another programs don't like? Might it be the physical size as measured in pixels? If you're scanning at 1200ppi and your photo is 4 X 6, the "pixel count" on that image would be over 35.5 million pixels. That might be what other software is complaining about!
This is an excellent site for getting information about scanning. You might want to read through it and see if you really need to be scanning at 1200ppi. <http://www.scantips.com/>
Please post again if you have more questions. I can think of more to say (I always can), but this might be enough information to get you past the present issue.