What you posted says
Hard Drive(s)
•ATA ST2000DM001-1CH1 SCSI Disk Device
◦Disk_Model: ATA ST2000DM001-1CH1 SCSI Disk Device
◦Disk_Size: 2000 GB
◦Disk_Partitions: 4
◦Disk_TotalHeads: 255
◦Disk_TotalCylinders: 243201
◦Disk_TotalTracks: 62016255
◦Disk_TracksPerCylinder: 255
I'm guessing one partition is the restore partition, one partition is the tiny diagnostics partition, one partition is your main Windows partition. The other partition could be an empty partition or it might be something like Dell's Media Direct partition.
If you click the start button and enter
discmgmt.msc
in the search box, it will open the utility that shows your partitions.
Don't change anything unless you know what you're doing, but you can look at the size of the partitions to see what they are. At least two of them won't be visible in Windows Explorer but will show up in the Disk Management Tool.
Dell Diagnostics is tiny -- in the MB's in size.
The restore partition may be about 10 GB.
The Media Direct partition (if that's what it is) will also be about 10 GB.
If you have two large partitions (in the hundreds of GB), one will be the Windows partition and the other is probably an empty partition.