Sat Nav reinstall questions

[R2D2]

Firstly, hello! This is my first post and im a bit blown away with the info available on this forum, so thanks to everyones contributions.

Right, the software on the MKIV nav in my e46 seems to intermittently crash (radio/cd cuts out, sometimes the nav doesnt start at all, sometimes the GPS gets stuck on 'please wait') and after days of reading up on the subject i think im ready to do an upgrade/reinstall, but ive got a few things that i cant quite figure out...

• What file format will the OS disc have? i 'aquired' both versions V31 and V32, but one is an .iso file while the other is a .mdf/.mds file? Whats going on?

• I have version 4-1/00 on my nav, but how can i tell which version (v31 or v32) that i currently have because if its V31, then i can just chuck V32 straight on, but if not ill need to downgrade to V31 first, then back up to V32 (i want to change the splash).