Splash Extention Difficulties

Im trying to use FireFox's Splash Extention, https://addons.mozilla.org/firefox/2995/ to create my own Splash page, but because it is on my portable drive, my drive letter sometimes changes, either from E:\ G:\ or K:\ depending on which computer I use, but the Splash Extention talkes the full file name directory ( E:\... image.jpg) instead of just (\image.jpg)

Thanks for your help,
Campsoup1988