To ensure that your E2B USB flash drive will boot from as many systems as possible, it should have the following characteristics:
- Have the boot partition marked as Active (bootable)
- Have grub4dos boot code in both the first sector (master boot record or MBR) and the first sector of the first partition (partition boot record or PBR)
- Have two primary partitions in the MBR partition table
- Have all boot files and E2B files within 137GB (128GiB) from the beginning of the drive
If you use the Make_E2B.exe GUI to make your E2B USB drive, then it will have these properties already.
It has been rumoured that some BIOSes will only boot from a USB FAT partition and not from an NTFS partition (although I have never seen this personally and I have never had any specific confirmation of this phenomenon!).
However, even if your drive is correctly made, some early PCs with USB 1.0 and early USB 2.0 ports may not boot to grub4dos\E2B.