VMware Workstation guest VM’s do not support booting from USB devices, (it’s not built into their “BIOS”). However there’s nothing to stop you booting to CD then using that to boot to USB.
1. Download the PLoP Boot manager from http://www.plop.at/en/bootmanager/download.html
2. Extract the downloaded zip file, and inside you will find an ISO image called plpbt.iso that’s all we need. You can delete everything else.
3. Set your virtual machine to use this .iso file as its CD drive.
4. Connect your USB drive to the guest VM by clicking VM > Removable Devices > The device you wish to connect > Connect.
5. Boot the VM with your PLoP CD, image and select USB from the boot options.