If you have a large (>128GiB) USB hard disk, I recommend that you use the first partition (up to 128GiB in size) for E2B and use the second partition for other purposes such as for storing utilities, hard disk backups, documents, etc. Note that only recent versions of Windows 10 (1703+) can access the 2nd partition if it is on a Removable (flash) drive.
However, you can place most payloads such as linux .ISO files, Windows VHD files, etc. on the second partition and add the PTN2_MNU.mnu menu file to one of the menu folders (e.g. add it to \_ISO\MAINMENU). The PTN2_MNU.mnu will take you to a sub-menu where all the files in the folder on the second partition will be listed and you can then boot to any one of them.
Note: Windows VHD files will only boot from partition 2 on a Removable USB drive if the VHD contains Windows 10 1703 or later. However, there should be no restriction if the USB is a hard disk.
The 128GiB USB BIOS bug
Note that due to some BIOSes (e.g. Asus EeePC's) having a bug in their USB driver, they are not able to access files past 128GiB on the USB drive. This bug is quite common, especially on older USB 2.0 only systems. This means that grub4dos will not be able to access the file if it has a sector address higher than 128GiB on the disk. This is why I suggest you do not use a USB drive larger than 128GiB - or at least keep the E2B partition below 128GiB in size.
If the file is beyond 128GiB on the drive (e.g. in a 2nd partition on a >128GiB USB drive) then grub4dos may be unable to access it.
E2B will warn you if the BIOS has this 128GiB bug as soon as it starts to load.
Sometimes, you can fix the BIOS bug by loading the grub4dos USB 2.0 driver which replaces the buggy BIOS driver (hold down the SHIFT key just as E2B starts to boot to load the grub4dos USB driver). However, the grub4dos USB 2.0 driver only works on older USB 2.0 systems and not with newer chipsets or USB 3.0.
Tip: If your system has this BIOS bug but does not have any USB 2.0 ports and you have a USB 3.0 E2B drive, then connect the E2B drive to a USB 3.0 port using a USB 2.0 cable - this may allow the grub4dos USB 2.0 driver to work because it will use the USB 2.0 connections instead of the USB 3.0 set of contacts.
Windows ISOs
You may have noticed that I said that you can place most payloads on the second partition - well Windows Install ISOs were an exception, but not now!
I have tweaked E2B v1.A7g so that you can, if you wish, add Windows Install ISOs onto the second partition (all types of Windows ISOs - except XP ISOs).
Here is how the 'cheat' works...
However, you can place most payloads such as linux .ISO files, Windows VHD files, etc. on the second partition and add the PTN2_MNU.mnu menu file to one of the menu folders (e.g. add it to \_ISO\MAINMENU). The PTN2_MNU.mnu will take you to a sub-menu where all the files in the folder on the second partition will be listed and you can then boot to any one of them.
Note: Windows VHD files will only boot from partition 2 on a Removable USB drive if the VHD contains Windows 10 1703 or later. However, there should be no restriction if the USB is a hard disk.
The 128GiB USB BIOS bug
Note that due to some BIOSes (e.g. Asus EeePC's) having a bug in their USB driver, they are not able to access files past 128GiB on the USB drive. This bug is quite common, especially on older USB 2.0 only systems. This means that grub4dos will not be able to access the file if it has a sector address higher than 128GiB on the disk. This is why I suggest you do not use a USB drive larger than 128GiB - or at least keep the E2B partition below 128GiB in size.
If the file is beyond 128GiB on the drive (e.g. in a 2nd partition on a >128GiB USB drive) then grub4dos may be unable to access it.
E2B will warn you if the BIOS has this 128GiB bug as soon as it starts to load.
Sometimes, you can fix the BIOS bug by loading the grub4dos USB 2.0 driver which replaces the buggy BIOS driver (hold down the SHIFT key just as E2B starts to boot to load the grub4dos USB driver). However, the grub4dos USB 2.0 driver only works on older USB 2.0 systems and not with newer chipsets or USB 3.0.
Tip: If your system has this BIOS bug but does not have any USB 2.0 ports and you have a USB 3.0 E2B drive, then connect the E2B drive to a USB 3.0 port using a USB 2.0 cable - this may allow the grub4dos USB 2.0 driver to work because it will use the USB 2.0 connections instead of the USB 3.0 set of contacts.
Windows ISOs
You may have noticed that I said that you can place most payloads on the second partition - well Windows Install ISOs were an exception, but not now!
I have tweaked E2B v1.A7g so that you can, if you wish, add Windows Install ISOs onto the second partition (all types of Windows ISOs - except XP ISOs).
Here is how the 'cheat' works...