$opening = "::wavewave::";
$echo = "There are many OS's out there that are small enough to fit on a thumb drive, but as they said, MS-Dos is the only one under 10 Megs. Windows has several OS's created for thumb drives, but I doubt they were built by Microsoft. XPE is one of them, around 500 Megs I think, and they have smaller, I currently have WinXP that's around 100 or so Megs. I'm a computer tech, and have to use them quite often. Can turn your USB drive into a bootable OS, most programs you download will come with instructions.
Also, there are many, many different types of USB Linux. From DamnSmallLinux, to Linux USB, to PenDriveLinux.
But of course, that is only if you want to use your thumb drives to run your computer, but I suspect you want a small OS to install onto your hard drive. And in all honesty any OS you find that is 10 Megs or under will not be an OS you'll want to use for very long. Most hard ware, almost all software, and almost every game will not work on that computer.
To install a full OS to your hard drive with out using a floppy, you'll need the OS (can be downloaded), and make your USB device bootable (can google it, will have to download some files). That way your USB device will become like a CD and CD-ROM itself. The full version of Windows XP is around 600 ~700 MB's.
If your computer does not have USB ports, then the only two options are MS-DOS on floppies, or buy/borrow a CD-ROM from any other computer temporarily, to plug into your computer long enough to install any OS.";
$ending = "Sorry for such a long post. There wasn't enough information in the opening post for me to give accurate information/advice on. Good Luck, and let us know how things go!";