Reattach data disk after Windows re-install???

Here's the setup.

Server running Windows, disk 1 has the OS, disk 2 has the data. You're running Hyper-V. You wipe the OS but don't touch the data disk. If you reinstall Windows, can you reattach the data disk without formatting the disk?

I just ran into this yesterday and was almost positive it would work. But Windows saw the disk as unallocated space and wouldn't recognize it without formatting.

Is this possible?