After installation, back up your C:\Program Files\Autodesk\AutoCAD 2010\French\ folder. Should your system crash, you can restore the language files without re-downloading the 400 MB pack.
The pack will extract to a temporary folder (e.g., C:\Autodesk\LangPack ). Do not interrupt this process. Autocad 2010 French Language Pack
No. LISP routines use command names, and AutoCAD 2010 recognizes both English and French command aliases internally. Your scripts are safe. Autocad 2010 French Language Pack
The installer automatically detects the AutoCAD 2010 root folder (usually C:\Program Files\Autodesk\AutoCAD 2010 ). Do not change this unless you have a custom install. Autocad 2010 French Language Pack