Updating your AVMAP IV is fairly strait forward if you take your time and back yourself up.
From the AVMAP WEBSITE:
''9. How to update the software?
In order to update your EKP you need a CF reader, you cannot update your CF without it.
First of all download and unzip the update files from our support section.
Enable the show of hidden files. Create on your Desktop the folder 'Old CF'* and copy in it all the files from the CF (is the backup folder if something goes wrong).
Omit to copy the 'CHARTS' folder. Create on your Desktop the folder 'New CF' and copy in it the same files you copied in 'Old CF'. Replace the files format swx in 'New CF' with the ones you downloaded from internet. Ovewrite the files in the cF with the ones in 'New CF' (do not touch the CHART folder).
Turn on the EKP and verify: if the procedure was correctly executed. If not, reinstall in the CF the files from* 'Old CF' and repeat the procedure.
NOTE! : this procedure can delete all user marks from the RAM. Save them first in the CF* with File Manager
If you have a problem, call them and the girl ( Sorry can't remember her name) is very nice and helpful and will talk you thru the steps..
P.S: Here a link to the download page: