Unused/unusable? Partition

[squallseifer]

I was backing up some of my fighting games onto my xbox stock hdd and i realised i was missing out on some space.
When i check in boxplorer i had something like 749mb on partitions x, y, and z.
Can i use these? Or should i leave them
Also if i can, would it be a good idea to re-partition the hdd so i only have C drive and E drive?