It IS possible to boot from a usb digital storage unit yes
Theres even a company selling micro-PCs which was my idea and got ripped off but oh well I cant say I worked for it (never patented anything).
They are the guys who created win98 optimizers (for making win98 lite, which is about 100mb or less, I got it down to 80mb if I remember well, for a customer's very old pc, he needed more space and didnt used all the craps win98se had so simply took them off and added some of my own PB programs for unzipping, etc. fully functional pc in 100mb -_-
Now adays theres SD cards of 1gb.
You can boot from a pendrive (which reads an SD card). but for making usb booteable you need a set of dos drivers (so kinda you boot dos, boot the drivers and once you got access to the usb drive as if it was a real harddrive, you boot windows) this was done automatically.
Its the fastest thing i've seen so far, but got no money for a 1gb SD or maybe 2 (imagine this: 1 of this SD you use it for the XP OS, of course, you will make it lite taking out all the stuff you dont really need, lets say you'll use this pc for a specific task, then take out all the crap you dont need. later get a mini atx PSU and motherboard, with a duron processor (meh i'd put the latest amd 64 dualcore if you ask me -but no money- ). then you got another usb drive with 1gb sd in, this will be your fast-access drive (for swap files, hibernation files, temp files, thats important to have a fast access drive and using another SD for this will make the job up to 1gb).
You could put all this into a small box (ala mini mac) but PC.
YES Its possible, but I dont have money for making a prototype.
YES Theres a company which made this, this is why im telling a rough of my basic idea, because its not really plausible anymore (cant make money out of this, ok I could but if they patented it already, im lost).
Seems that if you got a brilliant mind in this life, and got no money, its like having no mind at all. Get an investor ? nah no one believes in something they cant see

I wonder if someone would like to work on this, I have drivers and all software needed nor the latest hardware, nor the SD cards, because im cheap this year.
