Hard drive shows full with almost nothing installed on it!

Hard drive shows full despite almost nothing installed on it!  I already ran every cleanup tool under the sun.  Why would Dell sell us a PC with an 116GB hard drive that completely filled up just because we updated to Windows 11 from 10???  It is a Dell OptiPlex 3080 - micro - Core i3 10100T 3 GHz - 8 GB - SSD 128 GB.  PC has barely been used!  There's nothing on it to account for only 1.61GB free out of 116GB!  C: drive shows 116GB capacity but invoice shows it's a 128GB.  PC is completely unusable!  Can someone please help?  PC is a micro and not even 4 years old yet.  We don't want to have to buy a new PC!