So, the other day I happen to be somewhere and the only working laptop suddenly had a problem with Windows XP. It simply stopped working. People tried System Restore, etc. They simply needed a machine that could access the Internet for some clients and they were starting to panic.
I happen to have an old Ubuntu CD for version 8.04 and I offered to start the computer up using that CD. I didn't install Ubuntu - I simply started the computer using this disk and we were up and running very quickly with Firefox. You don't have to be a Linux pro to use Ubuntu. The interface is so simple that anyone can pick it up very quickly.
The lesson for the day is simple: keep a Ubuntu CD around in case you ever need to start up your broken PC.