Right!
One at a time. Step by step. This for scanning large images:
Scan slightly over a half at 100% and at 600 dpi. This will give you a raw image that you can edit in your software package.
Resize this in your package, probably on a drop down menu on the top bar saying 'Image' and then'resize', keeping the dimensions constant make the width about 800 pixels, the height should adjust accordingly.
Now, go to 'File' and 'Save As'. Save as <filename> and click on jpg and then 'Options' or a dialogue box will come up. This will show a sliding bar with 'high quality/low compresson' at one end and 'lowquality/high compression' at the other. Select High Quality and save to <fliename> on your desk top.
Exit your package and right click on the file and go down to properties or hover your mouse over the file. This should tell you the file size. What does it say.
This is a bit step by step but I'm trying to help.
Gadget