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#11
One of the Dell partitions is the various (several) recovery options if you ever need to go back to factory install or some in between step. Another partition is the Dell hardware diagnostics. Leave things alone. If you are desperate for more "C" drive space then upgrade the size of the drive. Also, before you do anything make a full drive - all partitions - disc image to a separate drive, so you can recover if need be. You should be making disc image backups anyway - for "When" its needed. If the drive would fail all your user programs and data are lost without it.
I work the Dell Community forums and see users delete OEM partitions and then when problems arise their only option is to do a fresh/clean install or if the drive fails, replace and do fresh install because of no backups.