Porteus is fast boot linux which can boot from a multiboot USB drive straight from an ISO file with persistence. This was suggested as a 'fast booting linux' version by futahorse on a reboot.pro here.
Porteus is a complete linux operating system that is optimized to run from CD, USB flash drive, hard drive, or other bootable storage media. It's small (under 300Mb) and insanely fast which allows you to start up and get online while most other operating systems are left spitting dust. Porteus comes in both 32 & 64 bit and aims to keep on the bleeding edge. It also supports several different languages and the user forum has language sections. Join the community now!
Here is how to create a Multiboot (Easy2Boot) USB drive (Flash or Hard Disk) using the 32-bit version of Porteus
1. Make an Easy2Boot USB drive by following Tutorial #72
2. Download the ISO file from http://porteus.org/distro-download.html current folder - I used Porteus-v1.1-i486.iso
3. Copy the Porteus-v1.1-i486.iso file to \_ISO\Linux folder on your Easy2Boot USB drive
4. Copy the Porteus-v1.1-i486.mnu file to the same folder - the file is at the end of the Tutorial #72 page
5. Run RMPrepUSB and select the Easy2Boot USB drive
6. Click on the Create Ext2 FS button and specify a name of porteus.ext2 and a filesize of whatever you desire (e.g. 300MB) - the size is up to you and will depend on how many files you may want to add to it once you have booted. Note that the filename porteus.ext2 must be all lowercase letters.
That's it - now test it by booting from a real system (or use the RMPrepUSB QEMU button or VMWare or some other emulator).
If you don't want to make an Easy2Boot USB drive and already have a grub4dos drive, simply copy the Porteus-v1.1-i486.mnu text to your menu.lst file and add this line to the top of your menu.lst file:
Note that you must place the ISO file in the folder /_ISO/Linux and note how some letters are in capitals and some are not.
Example grub4dos menu with 'cheat codes' for booting from an ISO file for Porteus (if you want to make your own grub4dos menu's)