Hello guys and thank you for your suggestions.
I went into my BIOS and changed some settings, such as "Disable secure boot" and something about UEFI and Legacy thing (it was set to only UEFI and I selected both UEFI and Legacy). After that, it enabled to boot from the USB with the windows 8.1 installation so I performed a clean install of it (had to re-download all of my applications and thankfully I have an external HDD of 1 TB, so all of my personal documents were not lost). Lenovo for some reason does not allow to boot from USB even if you change the priority thing, so I had to perform these tasks first in the BIOS settings.
Windows 8.1 Pro yayyyyyyy:
http://i.imgur.com/HIuJB6I.png
To answer some of your questions, my laptop is Lenovo B590 (
Link Removed ), and no, I had no recovery partitions, when I installed Windows 10, it performed an upgrade from Windows 8.1, so that I would not have to install all over my programmes (I have a lot of programmes, some of them are 30GB each in size, so it does take a whole day to install everything).
Using Windows 10, I had sudden problems, like some Windows service would randomly stop and I would have no sound on my laptop while I was watching Netflix or something else, and I had to perform every time a fix to restart this service, which was annoying. I love beta testing, but not when it has such major problems. I would also experience USB problems, it would not recognise my external HDD (only sometimes) or my mobile phone when I tried to transfer photos/music/videos etc., which makes it a big waste of time.
I was quite devastated when I saw that I have to re-install everything, but thankfully, now it's all good. I am not going to install Windows 10 again until its official release is out and after I've seen some feedback that in its official release, no major bugs like the ones I had exist any more.
However, thanks everybody for trying to help me out. At least I now know have a Windows 8.1 installation on my USB ready and I know what settings to change in the BIOS to make it possible to do it all over again, if I have to.
Some things I noticed however, after the Windows 8.1 format, my boot logo screen is the Windows 8.1 instead of the Lenovo. Can I change it back to the Lenovo one?
Furthermore, I now have a System Reserved Partition, which is 350 MB. Should I delete it using the command prompt or is it essential for my Windows 8.1 working? I don't mind it, I simply want to know what it is and if I should have it.
A print-screen of it:
http://i.imgur.com/v9XlxXM.png