I have an Inspiron 5680- Windows 10 latest version, 64bit- with a 125Gb SSD as the Primary C  Drive and a 1Tb hard disk D Drive. Am receiving notification of insufficient space to backup- which no doubt is correct since there is only 7Gb free space on the C Drive. Can I change the default backup destination from C to D Drive? If so how? If pertinent here also; I am mystified that the SSD- C Drive- is almost full. I have installed applications ammounting to no more than 25 Gb and have personal files of no more than 20Gb. In hindsight I should have installed the apps on D Drive but these would free up only 25GB! What could be hogging all the other space, which I may or may not be able to move to D so as to free up space on C?