Once again thanks for the replies. All back up was done manually not using any back up app. Up to using Win 10 as compared with Win 10 pro the USB HDD was readily accessible on Win 10 Pro. All files were backed up in their original format. PDFs as that, DOCX etc all in uncompressed form. The idea was to have a clean install of Win 10, so all files were backed up to this one drive. The other 3 back up drives were being selectively consolidated to this one 2 TB USB Western Digital drive, so no multiple back ups. Part of the info is on Dropbox but not to the extent of the newer files. I was hoping to use a friends computer that has Win 10 Pro on it but he is busy and gallivanting off to Sumbawa tomorrow, 12 June. The use of Easus data recovery is an extreme last resort, from experience the 2 TB of recovered files will need up to 8 TB of storage and file names will be lost. Again from experience that will be many months of work that I do not have. I will read up on EASUS Partition Recovery, its free and I have it on my computer. The criteria is I must not lose these files. At present the backup drive is NTSF and considered to be in top condition,no viruses and passed extended test by Western Digital Tests. The cable is good, the USB port is good. Ports test OK by manual checks opening hidden files on Device Manager. The USB HDD disk shows its size on Admin tools and as Unallocated. When doing the new install this drive was not connected to the computer just the SSD as C and a standard Western Digital 2 TB hard drive. All drives checked for virus all hard drives and USB HDD virus checked, extended test by Western Digital app and defragged. One fault that was indicated from memory in the Devices and Printer page as the drive was set as PnP and quick removal. At this point of time that fault does not show. Le Pingouin, thanks, I will look at those apps.Once again gents, thanks for your help.