I´d installed Tomcat 5.5.9 on my XP machine.

For running with JRE 1.4 I had to install the 1.4-compat file:
http://jakarta.apache.org/tomcat/tomcat-5.5-doc/setup.html
"If using a J2SE 1.4 JRE, the compatibility package must be downloaded and 
expanded inside the folder where Tomcat was installed."
--> there is no link to get that package, no link on the download page either 
(I found it via browsing the archive)


"expanded inside the folder where Tomcat was installed"
The archive contains as root director "jakarta-tomcat-5.5.9" which is not the 
directory I had chosen in the installer (c:\tomcat\5.5.9).
--> change the directory structure inside the zip 
 from: jakarta-tomcat-5.5.9\LICENSE... , jakarta-tomcat-5.5.9\bin\jmx.jar
 to  : \LICENSE... , bin\jmx.jar