Overgrowth Setting Writedir
From Wolfire Games Wiki
Setting the write dir on Windows Steam
To change your write dir on Windows and Steam to be something else than the default in C:\User\<name>\My Documents\Wolfire\Overgrowth perform the following steps.
1. Start Steam 2. Right click Overgrowth, select Properties 3. Click "Set Launch Options" 4. Enter the following: --write-dir C:\OvergrowthData
The path can be changed to pretty much anything, but should be limited to shorter paths to not overextend windows older 512 character path limit.