So there's a new notebook, which is empty. there would be a lot problem when i'm trying to install windows in its BIOS (so don't tell me to just install it from the notebook, cause i've been there, and a lot problem came to me, and don't ask what's the problem)
I have a PC, and I'm wondering if there's a way i could install Windows 7 on an empty External Hard Disk, then i put the hard disk back to the Notebook.
It's like installing somebody's notebook from my PC.
No. That's not going to work because the install is going to be installing system dependent drivers. It will find your PC and install drivers and registry settings based on your PC. When you later move the external drive to the notebook, those registry settings and drivers will fail upon boot up (because the PC hardware cannot be found).