SanDisk Cruzer blade 4GB being detected on boot but 8GB not being detected

I am trying to install Windows on my Laptop (Dell XPS 15) using a bootable pendrive. For this, I am using my Sandisk CruzerBlade Pendrive. The problem is that in order to install Windows 8 or 10 I need more than 4GB space. And for some reason the 8GB pendrive is not detected by my laptop. However, I have a 4GB Sandisk CruzerBlade as well and that is being detected and I am able to boot from it. But unfortunately, I cannot install WIndows 8 or 10.

Any ideas why one is working while other is not. My hard disk is clean at the moment so there is no OS. I am trying to create bootable Pendrives and install OS from the same. Thanks!!