I presume you both work on Apple machines, don't you?
These are the directories to clean from <synth> files:
Standalone ==> /Applications/Arturia <synth>/
VST ==> /Library/Audio/Plug-Ins/VST/<synth>.vst
AU ==> /Library/Audio/Plug-Ins/Components/<synth>.component
RTAS ==> /Library/Application Support/Digidesign/Plug-Ins/<synth>.dpm
Sounds and Prefs ==> /Library/Preferences/<more or less synth name>/