You might consider using Linux. There is a trick for getting Ubuntu on it -- which would be ideal for you as a user but you probably (almost certainly) don't know enough to pull it off. Debian is somewhat more difficult but -- assuming this has an ethernet port and you have a cable or DSL connection to the internet, and currently you have a USB stick (I last installed it this way two years ago using floppy disks) you can boot up into Linux, connect to the repositories and in about four hours have a complete operating system installed and working on your machine. Debian is slightly more advanced than Ubuntu. Okay, I know a couple of Ubuntu developers and everyone I've ever met is involved in interfaces for non-computer power users or security, or else they deal with the latter a lot. One of them made a joke the other day about how Ubuntu is Debian with Eye-candy, but it is a LOT more. I use Debian on this machine normally (right now I'm on a FreeBSD Unix Live CD) and I have to use the command line a lot, which doesn't bother me. Anyhow, this page will help you find netboot images for a USB stick. There is some information there on installing it. You want the netboot images. Connect the computer to the internet, boot it up from the USB drive, and follow the instructions on your screen:
http://www.debian.org/distrib/netinst
Once you begin downloading figure four to six hours.
This is more information about booting from a floppy:
http://www.debian.org/releases/2.2/i386/ch-rescue-boot
Here is one techie approach to installing Ubuntu:
http://efod.se/blog/archive/2006/11/29/installing-ubuntu-on-a-machine-with-no-cdrom-drive
A-HA!!! Excuse me. I finally found the EXACT information I was looking for. To boot from floppies first download these four images:
http://ftp.us.debian.org/debian/dists/etch/main/installer-i386/current/images/floppy/
Now get rawrite from here:
http://www.tux.org/pub/dos/rawrite/
rawrite2 is the fastest version. Rawrite 3 is if 1 or 2 fail.
Take 4 good floppies. use rawrite to copy the image files onto your floppies. Do NOT use diskcopy or any other tools -- there are formatting issues which rawrite is supposed to handle NOTHING else does. Plug your computer onto your ethernet connection, boot and follow instructions.
http://linux.simple.be/debian/etch/floppy
Of course if you want to get some major geek points, and have an easier distribution, here is how to install Ubuntu using the floppies you downloaded from debian:
https://help.ubuntu.com/community/Installation/WithFloppies
Technically yes, you can change Debian to Ubuntu whenever you like. Generally, don't. If you install Ubuntu over debian there are lots of files with scripts in them from Debian which will be orphaned, clutter up your disk and etc, If you know Linux you will know about Virtual Terminals -- once you are online (use dhclient eth0 if you can't connect at first) which you can access by hitting alt-f1 alt f2 or any function key through f7 at the same time as alt, and get a command line you can, with wget, ftp or some other program fetch that file with before the system demands it.
https://help.ubuntu.com/community/Installation/WithFloppies
In other words, you can install it instead of Debian with a little hacking -- also true of Linux Mint. But if you aren't familiar with installing Linux, then you might start with Debian which, obviously, is easy to get on, even if it becomes a formidable industrial strength behemoth after that.