Java

I downloaded Java form http://java.com/en/download/manual.jsp
chose manual install and change it to L:\Program Files\FirefoxPortable\Apps\firefox\plugins It installed and runs fine on my home comp but as soon as i try it in College it says that the plugin is not installed.
In College the Drive letter is E:\ not L:\ could that have any effect on java?
is so any suggestions? also i cant install Java from College couse i dont have Admin privleges.