For Scan Disk
Err Msg: ScanDisk - (C): Cannot continue due to insufficient memory. When other applications are running, finish them first and try again.
For Disk Defragmenter
Err Msg: Optimization error - (C): Cannot optimize the drive due to insufficient memory. Finish some applications and then try again.
To avoid this symptom, perform FDISK and set C: drive to 16GB or smaller.
If the error occurs to D drive, format the logical drive using FDISK and re-create D: drive again.