For example, you have a netbook or desktop that you want to install Windows 7/8/10 onto, but can’t use DVD or USB for whatever reason (or don’t want to, like me). This method will allow you to boot and install Windows directly from the hard drive. This guide involves plugging the hard drive into another working computer, preparing the hard drive, placing it back in the system, and installing Windows as usual.

This guide will work for Windows 7, Windows 8 and windows 10.

Part 1: Preparing the HDD with Windows  setup files.

– Connect the hard drive to another working computer.
– Format the hard drive to NTFS (Quick format works fine; multiple partitions also work).
– Copy the following from your Windows 7 disc:

Boot
Sources
Bootmgr

Part 2: Making the HDD bootable

Using Windows XP, Vista, or 7, open CMD as Admin (Windows key + R, type CMD, hit Enter)

Enter the following commands, (replace X with what applies to your hard drive):

diskpart
list disk
select disk X
list partition
select partition X
active
exit
X:\boot\bootsect.exe /nt60 X:

(See picture for example)

Exit and shutdown.

Note: If you’re working on a 32-bit system, and you want to install 64-bit Windows, you may get problems trying to run the last command (X:\boot\bootsect.exe /nt60 X:).
Solutions:

Use a computer with a 64-bit version of Windows

OR

A little trick that worked for me: If you have a 32-bit Windows 7 disc, you can copy bootsect.exe from that and replace the 64-bit one (boot\bootsect.exe).

Part 3: Booting and installing Windows

Place the hard drive back into the target machine. Make sure that the BIOS is configured to boot from the hard drive. If you did everything correctly, you should see “Windows is loading files” and setup will load (really fast, too, because it’s loading from the hard drive). Install Windows as usual (but don’t format your drive this time in the installer – otherwise it will erase the Windows 7 setup files too!).

Part 4: Final steps/housecleaning

We’ll have to quickly edit the boot menu once Windows is installed.

In Windows 7, hit the Windows key + R. Type msconfig, and hit Enter.
Click to the Boot tab at the top.
Click ‘Windows Setup (\windows)’, and hit Delete.
Click OK.
Click ‘Exit without restart’.

And lastly, delete the ‘Sources’ folder from your hard drive root (this will free up 2-3gb).
I hope this helps some people out.  Feel free to comment 🙂