RobotStudio event

How to install a system with USB flash disk?

Hi,
I prepared a system with RobotStudio 5.15.02. Than I copied it a flash disk and I put on IRC5 main computer USB port.
I did X-Start IRC5. When I selected install system, controller didn't find USB disk. Error: No media found.
I tried Fat16, Fat32, NTFS file system, 4 different flash disk from 128MB to 4 GB.
But I didn't . It is possible with computer but I would like to do it with USB.
Existing RW on IRC5 is 5.10.
Do you have any idea?