Make sure all software is up to date
1. Throw everything from desktop in trash except links.
2. Check all remaining links to make sure they work.
3. Finder/Downloads/type disk in search box. Select Disk Image from drop down box. Delete all files that end in .dmg (drag to trash)
4. Finder/Go/Documents/drag all to trash
5. Press command-space (spotlight will appear) type in search box - Mail downloads. Click on mail downloads - select all files and drag to trash.
6. On finder window Go/Go To Finder/
type in /Library/Caches press enter. Drag all files to trash.
7. Click on Safari - History/Clear History (will be at bottom)
8. Click on trash can/empty trash