Nady, I'll try to answer number 2 first. If your are scanning magazine pictures, you probably are seeing the moire effect. Some scanner software allows you to set the adjustments to correct this. Check the documentation that came with your scanner. My HP scanner attempts to remove the moire automatically and does a poor job. Thus, I have to remove it in Paint Shop Pro. It's been a while since I used version 5 of PSP, so I don't remember the approach that version took. But version 7 has a moire filter that works very well.

As for 72 vs. 300, personally I prefer to scan at a higher setting -- 300 may be too much -- and then resample down in Paint Shop Pro.

Bob