When you say that the function doesn't work, do you mean that it doesn't do anything or that it fails to find the backup?
If it is the former, consider reinstalling OneCare and trying again or contacting support.
If it is the latter, we've found that this is often solved by configuring backup on the PC that you are trying to restore to. Configure it to perform a small backup, selecting the 'what' for a type of file that doesn't exist on the PC in large volume. Point the backup "where" to the Share on the network that you wish to restore From. After the backup completes, run the restore wizard and select the option to restore from another PC as your reinstalled OS is a new PC to then backup process.
If you continue to have problems, please contact support;
How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
-steve
Microsoft MVP Windows Live / Windows Live OneCare Forum Moderator