I backup my Server 2008 R2 system drive nightly using automated backup tasks (created by R-Drive image)
In the last few days I encounter failures such as "Specified parameter is invalid.: Partition 11:1 is not found ". Upon further investigation it turns out that the drive number assignments are potentially changed by Windows on every boot. See: http://support.microsoft.com/kb/937251
Since R-Drive uses drive numbers for specifying the backup source, this can not only cause failures but is potentially dangerous since another drive may be backed up instead of the one specified while creating the script. Also I could not find any option in the GUI to specify logical drive *names* which are supposedly constant.