I have been having problems with LW hitting major slowdowns and lockups (though my computer has never completely locked up). Is it ok to have more than one version of JRE installed at once?

I have:
J2SE Runtime Environment 5.0 update 2
Java 2 Runtime Environment Standard Edition v1.3.1_04
Java 2 Runtime Environment , SE v1.4.2_07

I haven't manually installed any of these and the info is from the Add/Remove Programs panel.