Is this Windows 7 a retail version, you purchased seperately? Then install the HD & do a Fresh install, to get the correct drivers loaded into the OS.
If it is an OEM OS that came with a prebuilt system (HP, Dell, etc) can't be done, the OS is tied to the OEM's motherboard, & can't be transferred.
If it's an OEM version you bought, maybe, after the install, you will need to call MS for activation & it's up to them.
MS can tell if the OEM is 'bought' separately or from an OEM such as HP, Dell etc.