Thistutorial is for Ubuntu 11.04 or later (Natty Narwhal - first screenshot below) but also works for 11.10 (2nd screenshot) if you change the iso name and 12.04. You can make a persistent version (2GB+ USB stick or USB hard disk
required) so that any changes you make will be remembered (e.g. wireless
WEP/WPA settings, country, wallpaper, etc.). In addition, once you have created a bootable USB stick - you can
use it to install Ubuntu onto a PC (or even dual boot on a PC).
Boot from ISO
Do you want to have apersistent OS but run from an ISO file and use grub4dos and have only 4 files on your USB drive? No Problem!
Download and copy the single file ubuntu-11.04-desktop-i386.iso (or 12.04 or 15.10, etc.) to a new folder on your hard disk (e.g. C:\Ubuntu) or if you have a FAT32 USB drive already prepared, copy it to the USB drive.
IMPORTANT: If you are not making a new USB drive, make sure that the ISO file on the USB drive is contiguous. Use RMPrepUSB (latest version) and press CTRL+F2 or run WinContig on the ISO file or whole drive. If the ISO file is not contiguous, grub4dos will attempt to load the whole ISO file into memory and you may not have enough memory in your system.
Make or add these lines to a new menu.lst file in the same folder, contents are as below:
Note: if you want a persistent filesystem then keep the word 'persistent' in the command line and make a casper-rw file in step 5.
Format your USB drive using RMPrepUSB (v2.1.605 or later) - FAT32 + Boot as HDD, set the 5 - Copy Files source to the C:\Ubuntu folder of your hard disk - click 6 Prepare Drive and wait for it to finish. If you already have a bootable USB drive with grub4dos and a menu.lst then skip this and just copy over the ISO file and add the menu entries to your existing menu.lst file.
Note: Ubuntu 13, 14, 15 will work on both FAT32 and NTFS with persistent cheat code if you use the partnew workaround below. For Ubuntu 15 you need to run vmlinux.efi instead of vmlinuz.
Run Install grub4dos and install a grub4dos MBR (answer='Yes') and allow it to copy the grldr file over. If you already have grub4dos installed then do this anyway as you will get the latest compatible version - older versions of grldr may not work.
If you want a persistent filesystem to keep all your changes, make a new /casper-rw file (volume name and file name must be casper-rw) using the Create Ext2 FS button in RMPrepUSB(size of 1 to 4 GB recommended if you have space).
Using persistence with NTFS
PLEASE NOTE: Many linux versions (including Ubuntu's) will not automatically mount a persistent filesystem if it is a file on an NTFS filesystem (i.e. if your casper-rw file is on an NTFS USB drive then it won't work!)
However, there is a way around this.
First create your casper-rw file as explained in Step 5 - the file name can be anything you like (if you also change the menu.lst file too) but the volume name of the filesystem MUST be casper-rw.
Next rename the casper-rw file to a suitable name (e.g. Ubuntu1204-rw) - this step is optional but it avoids any other linux you have trying to use casper-rw - you can thus have many linux ISOs that all try to use 'casper-rw' on the same USB boot drive.
Ensure that the file is contiguous (run RMPrepUSB - Ctrl+F2 on the drive)
Now add an extra line to the beginning of your grub4dos menu as a line just under the title line (make sure the file name matches the one you created), as follows:
partnew (hd0,3) 0x0 / /ubuntu1204-rw
IMPORTANT: This will wipe the 4th partition entry of your boot disk! Make sure that the 4th partition table is empty (use RMPrepUSB - Drive Info - 0 to check).