Can we use external hard disk as Internal

Solution 1:

You can use your external hard drive as replacement of your internal hard drive. What that means, you can disassemble your hard drive enclosure and take out the hard drive, then install it in your laptop as a replacement of the faulty one.

So, you only need to know what type of external hard drive do you have ? is it 3.5" or 2.5" ..etc. if is it 3.5", then you won't be able to do the above method since 3.5" can't be installed on a laptop due to the hard drive physical size dimensions. (2.5" is the standard physical size dimension for laptops internal hard drives.).

NOTE: usually, 3.5" external drives has a power supply (charger) that won't turn on unless it's plugged into the wall, while 2.5" or smaller drives don't.

If you don't want to go through all that and you need to boot from your external drive instead. You can make a USB bootable Windows using a third-party tool like WinToUSB is doable solution, but not permanent.