just want to check that i can duel boot win 8? in short unplug my win 7 drive and install win 8 on a separate new drive. plug back in and choose between 7 or 8.
No. You would want to keep the Windows 7 drive connected if you want to have it automatically included in your boot manager at startup to select between them to run at startup.
Windows 8 will be set as the default OS to run at startup since it was the last one installed, but you can use the tutorial below to change that if you like.