You may not want to install Trisquel alongside Microsoft Windows even as a
means of helping yourself transition. The problem is Microsoft doesn't play
nice with others. You will likely turn on your computer one day and discover
the system doesn't boot. It is recoverable although not without a bit of
work. If you go this route hold onto the install CD as it will comes in handy
for recovery. If you have a few dollars lying around you can get cheap system
that will run Trisquel better than your current system (most likely).
I head ThinkPenguin.com and we donate 25% of the profits go to the Trisquel
project.
http://libre.thinkpenguin.com/
The Penguin Wee starts at $249 (no monitor / keyboard / mouse included) and
should work fine with the Trisquel LTS release. Although I'd suggest more ram
than the base configuration. The upcoming Trisquel LTS release is going to
need more than 1GB.