The noise that I could make out is extremely faint and could be a normal sound of the drive accessing data. When a drive is going bad you won't have to guess if it is making noise. The clicking will be loud and constant. But if you are concerned run a system diagnostics. Restart the system and at the Dell splash screen start tapping F12. Run full system diagnostics paying attention to the hard drive results.
As for the used space discrepancy, that is normal. In one instance you are looking at Disk C: properties. In the other instance you selected all of the programs and folders on the drive and expected the used numbers to be the same, and they will not. In my system I have about 256 GB used space under drive properties on the C: drive. But if I select all of the folders and programs I have 229 GB used.
This link refers to Windows 7 but the operation is the same for Windows 10. And as for which one to believe, use the Local disk properties. When you select all of the folders and programs, not all hidden system files and folders are detected.
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