Using the same Drive Internal & External

Hey so this is what I want to do.


I want to use the same drive for an external media library and internally as a os expansion for installed games.


My problem.


Everytime I use it externally and format it. I'll then put it in my hotswap bay (Haf XB). Windows prompts me to format it in order for it to use


I've tried partitioning it doesn't work.



I was wondering is it possible to use a harddrive Internally when you want and externally when you want. Without having to format. I've now tried NTFS formats and FAT32 to achieve this and neither have worked 



Thank you!