Full System Scan Question

I was running a Norton full system scan today, and when it got to the end and was scanning the D drive files, in the middle of scanning the D drive it went back to a few files in the C drive (a few files from itunes) and it already scanned itunes and music files in the beginning half of the scan.

I was just wondering if this can be normal for it to go back to the C drive in the middle of scanning the D drive. When it gets to the D drive it usually just scans D drive files until it is done.