In Windows, CrashPlan relies on the system user's read/write permissions to access your files. However, there are some files or directories the system user may not have permissions to access. Alternatively, your organization's systems administrator may have removed the system user from the permissions list.
If you need to back up these files or directories, then follow this tutorial to re-add the system user to the permissions list.
The CrashPlan app on Windows computers
After you update your permissions, you can tell CrashPlan to verify your file selection "now" and re-scan to back up the files.