Norton Disk Optimization
is essentially a defragmenter.
How to tune-up PC performance with Norton 360Defragmentation
Norton 360 can keep your PC tuned up and running smoothly by using a variety of techniques, such as optimizing your hard disk and deleting unused temporary files.
is a process that rearranges and reassembles your files on your hard disk. Over time, Windows will slowly fragment the files on the hard drive and store parts of each file in random physical locations. As this happens, the files will take longer and longer to access so deframentation becomes necessary to improve performance. See the The Importance of Disk Defragmentation
If you check the Norton Community forums, you will find numerous complaints about this feature and Disk Optimization alerts: Drive B: Other Error
with recommended solutions.
There are even more complaints about the amount of time it takes to run. The main thing that keeps defrag from running successfully is having other programs running in the background including your screensaver and anti-virus program. This also explains why you may receive message alerts during Disk Optimization. In response to these complaints, Norton provides this article: Norton 360 Disk Optimization takes a long time to run
The length of time it takes to complete deframentation depends on the operating system, size of the hard drive, number of files to defrag and defragmentation utility used to perform the task but it can take several hours. Once you start the defrag process, you should leave the computer alone as defragmenting utilizes a lot of system resources and will slow the computer.
If you want to disable Disk Optimization, follow these instructions