I have been using a SanDisk 256GB thumb drive on my Mac for years. I just tried to use it on my Windows 7 laptop, and it did not work. I plugged it into the USB2.0 port. The drive did not show up in File Explorer. I could however see the drive under Disk Management. In fact, I could see 2 partitions; a 200MB EFI partition and one other partition. I tried deleting the two partitions. I was only allowed to delete the larger partition, and I could not delete the EFI system partition. Then I was stuck. I could not create partitions or re-format the thumb drive.
Here’s what ended up working for me. I had to plug the thumb drive into my Mac. With Disk Utility, I right-clicked on the SanDisk Ultra Fit Media (not a partition) and selected Erase. A dialog popped up and I entered a Name, selected exFAT for the Format, and Master Boot Record for the Scheme. That completed very quickly, and then I was able to see the drive on my Windows 7 PC immediately after plugging in the drive.
I hope this helps others with this issue.