Wow... Older is a good choice of words.
The software for it is available on the BlackBerry web site.
https://www.blackberry.com/Downloads...969043751320TR
It is v2.7. You will also need Desktop Manager from the same BlackBerry.Com web site.
The R900M does not need a mobile charger, since it uses one "AA" battery. No charging at all. Just replace the battery.
You are going to need a program called "Programmer.EXE" and use that to delete all of the data and programs.
Not sure where you can find programmer.exe