Last night, after posting my inquiry to this forum (actually a desperate plea!), I collapsed in bed without turning off the desktop computer. This morning, when I rushed down to my desktop, to check for any responses to my post, I found that the icon on the LaCie external drive was no longer blurred, and that all of the files that had been unavailable, last night, were now available! When I conducted a search for the location of the Defraggler program file, I found that it was not in the Programs or Programs (86) folders on the C:\\ drive. Rather the program file was located in the Programs folder of the Windows folder's Start Menu. I inferred that the Defraggler program had run automatically after installation, and that it had been running during the period of time when the LaCie drive icon was blurred and files contained in its various folders were showing as "unavailable." I have concluded that the defragging process of the C:\\ drive (which is an SSD and which is not very large) had completed, and that the 1 TB external LaCie drive - which is large and was quite full of data - was still in the process of being defragged during the time, last night, when I was trying to access the files for the charity fund-raising events. Hence, the blurred icon and unavailability of so many of its files. In addition, I suspect that the double listing of the contents of the LeCie drive in the C:\\ directory is an means for enabling the Defraggler program to dissasemble and, then, reassemble the contents of the drive, during the defragging process. This morning, when I open the This PC folder, the LaCie drive's icon is sharp, there is no double listing of its contents, and every file that I have checked is now available. This implies that the defragging process was completed during the night, and that a significant amount of space on the LaCie drive had been cleared by the process.
I want to express my gratitude to Andrei CCleaner and nukecad and Willy2, for responding so quickly to my post/plea, and for offering their helpful advice. I cannot overstate the sense of relief that I am experiencing, and the renewed confidence I have in the competence of the CCleaner organization. Thank you.
May I make one suggestion: if the Defragger program is designed to run automatically upon installation, that a note be added on the installation panel, indicating that this is what will happen; or that there be options for setting when the program will run. I was suddenly called away from the computer, just when I was installing the three premium programs accompanying the CCleaner update and, if there were any such option(s) on the panel, I may have overlooked them in my haste. In answer to your quesion, I did open and run CCleaner, but did not use the Driver Updater or the Registry Cleaner, I only opened the CCleaner program, clicked the Health Check box and, while that was running, checked that the updated version that had installed.
Again thank you for your helpful responses.