Windows10 "Windows could not complete the installation. To install Windows on theis compuiter, restart the installation."

how can I switch to the usb? pls reply

When the CMD window opens it is set to the imaginary X: drive.  If you type C: it will switch to the C: drive which may or may not be what is normally your C: drive.  If you then type DIR then press enter you can see the contents listed.  Work your way up through the alphabet following this procedure until you find your USB.  You can only recognise it through its contents, one of which sill be setup.exe. the file you need to run.

Or you can try the method given by jderijke.

Go to the USB drive by typing the drive letter, typically D:

My drive was not mounted to D: (nor E:). I found out the drive letter using the command

    C:\>wmic logicaldisk where drivetype=2 get deviceid, volumename, description

 Turned out my drive was mounted to J: (!?)

I logged my experience with this problem here.

how can I switch to the usb? pls reply

I am posting to say that the solution given by DatayYC (on page 2) worked perfectly for me.  I was able to restart and complete the setup (Windows 10 v 1709) and all my installed software and user data was preserved (as indeed it should have been had things not gone wrong).

To follow DataYC's method you need to use installation media (USB/DVD) for the version of Windows that you were trying to update to.  So if you don't have that already you need to run Microsoft's Media Creation Tool ( https://www.microsoft.com/en-gb/software-download/windows10 ) on another computer that is actually working and choose the option to create bootable media.  But with bootable media the rest was easy and straightforward, as per the instructions given.  One piece of advice, it might be a good idea to take a quick look at the contents of the installation media on the working computer before you start, so you recognise it again when looking for setup.exe.  The drive letter assigned to it will vary from one machine to another

Here is the fix for "Windows could not complete the installation:

So I managed to get it started up. I turned the computer off and on 3 times to start advanced recovery. Choose advance options.  I was about to restore windows (reinstall windows and removing all apps and programs by keep personal files). Select reinstall and keep personal files. And then on the next screeen hit cancel.  So I hit cancel at the next prompt. I then selected start windows and it continued installation as normal without the error.

Thank you so much for posting this. I was about to reinstall windows, and this advice got my machine back and past the error. It did take quite a while to finish up the upgrade, but well worth the wait.

Such a huge thank you!!