well I suppose you don't know what GNU/Linux operating system is...
It's "not unix", but it's also
absolutely not Windows.
the GNU/Linux operating system, which is commonly mis-named as "Linux", is a free UNIX clone operating system. It's mostly using GNU software with Linux as the kernel. As it's free everyone can make their own version of system, currently the most popular version is Red Hat Linux (which is only available for purchasing). If you want to download a version, you can download Debian GNU/Linux 3.0 r3 at:
http://www.debian.org (the size is as big as 7 cds as it contains tons of software)
There's also a version at free software foundation's ftp server, which is much smaller (only 1 cd):
ftp://ftp.gnu.org/gnu+linux-distros/...86-pentium.iso
to install it, you'll need a CD-RW drive to burn the ISO images to CDs. then boot from the CD and follow the instructions.
(another thing is MS Visual C++ doesn't work on GNU/Linux
)