I've moved your post to the Home and Home Office are. Hopefully a product expert can help you soon.
It's possible these are just very large files and taking an extraordinary time to scan on a system which is slow due to other issues. If you go into SecurityCenter and click Navigation (top-right corner), then click Scan Your PC, then Run A Custom Scan.
Let's try unchecking exclude ZIP and other compressed files and try the scan again?
Please let me know if that helped.