Thorough Formatting of pre-partitioned HDD of Lenovo Y50-70

[Dabidou]

I have a Lenovo Y50-70 with HDD pre-partitioned as shown below, and I am fed up with the extremely slow performance of the machine despite my recent purchase of it.

The main point I don't know how to handle is how to completely format the HDD and reconstruct the EFI partition for keeping the BIOS functionality proper before installing a fresh copy of windows 8.1.

Regards

 

[SuperSoph_WD]

Oh, wow, Dabidou!

That's quite a number of partitions. No wonder why your performance is so slow. Honestly, I wouldn't temper with the partitions manually, so I'd suggest to go right ahead and clean install Windows 8.1, just make sure you backup any data from your PC before proceeding.
Here's a tutorial that might help you through the process: http://www.eightforums.com/tutorials/2299-clean-install-windows-8-a.html

Good luck! Let me know if there are any complications!
SuperSoph_WD