Question on Tranferring OS

In other words will i still be able to use the hdd for storage while keeping the OS on it,

Yes you can use it for storage and still be able to boot into Windows from it should you need to.

However, you must remember that it will be much easier to accidentally delete something that Windows might need in order for it to run properly, since those files will no longer be locked or in use. So be extra careful when deleting stuff on that drive.

Also, don't allow that drive's free space to get too low, otherwise Windows on that drive may not have sufficient free space to run properly when you need to boot from it.