My thoughts are leave them alone as altering any partitions may prevent the recovery program from working.
I think the first partition will have the recovery program that would allow you to restore the computer back to factory default or possibly rectify other problems without using the recovery disk/usb which you should have created.
The second partition may have the system boot files. Without these the computer will not boot into windows. The reason they do not have a drive letter is to hide them preventing anyone from deleting, altering the files or filling up the partitions.
The last partition may have the recovery files that the first partition would need.
If I'm wrong some one will correct me.