Can't Remove "Previous System"
The message "Item ____ is in use" is an indicator to a possible solution that you don't appear to have tried, which is finding out what is using this file.
- Go to Trash.
- Find the folder and right click.
- Select 'Put Back'
- Clear the Trash to ensure it was actually the Previous System folder.
- Go to the 'Previous System' folder
If there is a lot in this folder you'll need to do the following steps:
- Delete something.
- Try emptying the trash.
Keep doing this until you find the thing(s) that are blocking you from emptying the trash, try to associate them with an application that is running on your computer.
- Quit that application using the application interface or Activity Monitor.
- Try emptying the trash again.
If this works, great, if not you should contact the software vendor, or come back here with a follow up or new question.
Tips
In Finder you can quickly delete something to the trash using ⌘ + ⌫.
In Finder you can quickly empty the Trash using ⇧ ⌘ ⌫.
It looks like you jumped ahead to some steps that aren’t needed. Apple recommends these steps:
- Quit any programs you know were using the file, then try emptying the trash.
- If that doesn't work, restart your computer to kill off background processes, then try emptying the trash.
- If that doesn't work, restart your computer in safe mode by holding down the shift key as it boots to prevent login items and automatically launched programs from running, then try emptying the trash.
- If that doesn't work, restart your computer in Recovery mode by holding down ⌘-R, and when it boots, select "Disk Utility". In Disk Utility, use the "First Aid" feature to repair the disk containing the file you wish to delete. Then reboot your computer and empty the trash.
That is the end of the advice in the linked article from Apple, but if all that fails, make a Time Machine backup, erase the drive and reload your data. If Disk Utility and Safe Mode don’t clear things, it’s usually more hassle for trained mac admin to diagnose and fix than erase and reinstall.