During install, PC Backup scans your harddrive and categorizes all of your data files into backup sets such as word processing documents, digital photos, music files, and so on.
So as to not waste your bandwidth, PC Backup does not backup your operating system, application, or temporary Internet files. These files are best restored by reinstalling the software so that they are configured correctly with your system. Other files PC Backup omits are disk images (.iso), virtual drives (.vmc, .vhd, .vmsn), system configuration and driver files (.sys), and application files (.exe, .dll).
If you would like to backup system files/folders navigate to Advanced Tab and check the box Allow backup and display protected operating system files. Then click OK and restart Online Backup application, the folders will become visible.