I need an insurance policy to cover medical expenses etc in case of a
car accident while driving from Mexico to Canada 1st through 5th April
2005. I'm not looking for automobile insurance - I have that covered.

Where do you live and have your car insured?  If you have normal
medical insurance, ask you agent.  Some auto clubs have accident
policies that cover emergency medical care as a result of an accident.

Since you will obviously be in at least 2 countries of which you are
not a citizen, that is a wise decision.  Most auto insurance plans
will have only limited cover for medical care, and possibly none while
in a foreign country.

A very reasonable travel insurance plan can be found at
http://www.bpbinsure.com/global.htm

It will not only cover you for accidental injury sustained in an auto
accident (or otherwise), but will also cover you for illness,
emergency evacuation, emergency reunion, and repatriation.  However,
any prior pre-existing conditions will not be covered.  Have a safe
and fun trip!

I used http://www.worldtrips.com before and they have been great. I am
just throwing this out there for future reference. They are
underwritten by Lloyd's of London I believe.