If the drive is fine then there is no good reason why you can't continue to use the old hard drive.
You will, however, probably want to format it first, because if you don't it might cause a lot of errors with an operating system installed that will conflict with the motherboard and stuff.
If you just delete the Windows directory on it that may be good enough, but it would be best to format it that way there is no MBR on the drive.