Does the USB boot or are you booting from windows and trying to install via the USB--if so, I can see why windows may not allow a USB device to see undefined (to windows) partitions..
I might try boot from windows, unallocated (empty, no label) that partition, either leave it unformatted or pick a default type that is good cross platform (when detected by a boot), such as FAT32
The other issue is logical partitions (they exist withing a real partition on the hard drive)
--the easiest format for an OS is physical partitions (primary); of which there can be 4 on a any hard drive: a consequence of DOS partitioning scheme during PC development ..(historical and exists even today, for a BIOS based boot)
https://en.wikipedia.org/wiki/Disk_partitioningI also don't see how the two images you show match, first one, various windows OS partitions totaling approx 200+ GB of storage, of which you say you have removed approx. 50GB for Linux
--second image shows 320GB for /dev/sda
So /dev/sda is a total drive, not /dev/sda1 or /dev/sdb1, so no partition showing
--I can't get your image1 + image2 to total (ADD TO..) to GET APPROX. 320GB ?? [/list]