You don't currently have permission to access this folder

So you mount an external disk, try to go to the directory where you need to go and Windows tells you that you don't have the permission to do that.
I never understood the philosophy of Windows security, probably because I'm used to Linux. I don't want to understand it anyway unless it gets in my way.
What I tried successfully is:

1. Open the folder's Properties.
2. Go to Security and click Advanced.
3. Change Owner: Enter the object name to select and do Check Names.
4. Check Replace owner on subcontainer and objects.
5. Ignore the Windows security warning.
6. You're done!