I was trying to make a Ubuntu bootable USB disk; and attempted to use my SanDisk 4GB flash drive. Unfortunately SanDisk comes with pre formatted file systems FAT32 and CDFS file system. I could not remove the CDFS file system using Windows disk management tool.
SanDisk gives a removal tool to remove this CDFS file system, using this I was able to remove the file system from flash drive.
Here is the link to removal tool
I will attempt to make a Linux bootable flash drive