XPS 13: cannot install Windows using official USB

I want to be able to install Windows, using a Dell USB stick I received after my motherboard was replaced by a Dell technician. However, when I try to boot the USB I notice two things:

- The USB stick does not show up in UEFI mode:

the entries "wi" and "win" are custom entries added by me, to point to the UEFI file on the USB disk. If I boot from this, I get the Dell Logo and nothing happens from that point on.

- In Legacy mode I can boot from the USB, but I get the following error:

"There isn't enough memory available to create a ramdisk image"

I have 8 GB of memory, so this should not be a problem. I have confirmed by the system test in the BIOS that my memory works. My Windows partition on my HDD has been removed, but this should not be a requirement to install a new copy (or at least I hope it isn't).