To change/add/delete words form a Symbian phone you need to get access to the file system. This can be done with the use of FExplorer (other file browsers). You need to manually sign the application to install it, this can be done online http://www.symbiansigned.com/ where you enter your phones IMEI …
I found an blog with a guide to change the cover on your Nokia E50. Link PDF: step-by-step-guide-to-making-your-own-nokia-e50-metal-black.pdf (542,96 kb)
When trying to install a program on your mobile the program can be limited to a specific time period. If you try to install the program after this period you will get the error “certificate expired”. In some cases there is a workaround to solve this problem so you can …