USB Drive not mounted aka Y drive missing

I have being making bootable usb drives of win7pese 32bit for quite some time. However this is 1 of the few times I encounter such problem. My usb drive is not mounted. I tried adding the usb chipset drivers and it does not help. Normally, using the same usb drive, I just added in Audio, Video and network devices drivers. However, this time, the usb drive is not mounted at all. Can someone please advice?

I created the bootable drives using rufus.

I managed to get the usb to be mounted. Seems like it is having problem with the skylake. Installing the missing drivers will get the drive mounted.