If you're on dialup, then don't bother with this approach.
If you have broadband Internet (cable TV modem or ADSL modem), then
download a CD from here.
(Take "10.04LTS" version, for the easy to understand user interface.
The 32 bit version will run on more hardware, if you choose it.
Many of these downloads, will be in the 700MB size region.)
http://www.ubuntu.com/download/ubuntu/download
There are 500 different Linux distributions, and that is just one
of them. When 10.04LTS is no longer supported, I will no longer
be promoting that site.
I use things like that, mainly for testing, or for special (hacking)
projects. My regular desktop is not Linux.
Your laptop, is potentially a "business laptop" and has a TPM chip.
A previous owner may have installed some kind of security software,
and TPM can be used to enforce the need for a password, or for
preventing anything but the original OS from loading.
There are many more "failure" scenarios for used business laptops, than for
other laptops. For example, the BIOS of the laptop, could
do MBR substitution during the boot process, to support more
than four primary partitions. Only an "IT guy" can keep track
of stuff like this (fixing business laptops every day).
Paul