If you don't have admin rights at all, boot into SystemRescueCD (you don't need graphical mode this time) and follow the instructions for GNU/Linux. In SystemRescueCD all commands are run as root, so you don't need to add any prefix to the commands.
-If you normally use Windows, you maybe don't know the name of your USB disk in GNU/Linux. If that's the case, don't specify any disk in the first command. It causes parted to tell about all disks in the computer and you should be able to identify both the right disk and the right partition.
-After creating the disk image and booting into Windows, make sure that the filesystem of the partition where you plan to put the disk image is FAT32. If you don't know the filesystem, open My Computer, right-click the partition and select Properties. Then read the "File system" column. If there reads anything but FAT32, check other partitions of the disk too, if the disk contains multiple partitions. If you have a suitable FAT32 partition, continue from this step.
If your disk doesn't contain any FAT32 partition, but it contains a partition which is big enough and doesn't contain any important data, format the partition as FAT32.