loading RMySQL - location of MySQL install

I am having trouble loading RMySQL after installing it.  I have looked 
at archived r-help files and it seems many people have had issues, but I 
didn't find my specific issue.  I also went to the webpage at Vanderbilt 
(http://biostat.mc.vanderbilt.edu/wiki/Main/RMySQL) and followed the 
instructions as best I understood them:

     - I created a file called Renviron.site under "etc" in the R 
folder.  In it, I tried to put a pointer to where MySQL is.
         I tried:
             - MYSQL_HOME=C:/PROGRA~1/MySQL/MYSQL~Server~5.5/
             - MYSQL_HOME=C:/PROGRA~1/MySQL/MYSQLS~5.5/bin
               (which are guesses at how this should be written from the 
example on the webpage.)
             - MYSQL_HOME=C:/Program Files/MySQL/MySQL Server 5.5
               (the actual location; n.b. adding "\bin" yields the 
location of the mysql.exe file)
     - I then re-start R and attempt to load the package.
     - I get the following error messages:

Loading required package: DBI
Error : MYSQL_HOME was set but does not point to a directory
Error : .onLoad failed in 'loadNamespace' for 'RMySQL'
Error: package/namespace load failed for 'RMySQL'

Does anyone know how to write this so that it does point to the 
directory properly?Or, what else might be the problem?

Thanks,
Jeff

PS, I am running windows XP media edition and R 2.10.1, if that matters.