Unofficial repacks may lack essential dynamic-link libraries (DLLs) required to save changes securely. This can lead to corrupted SharePoint workflows, broken site templates, or data loss on your live SharePoint server.
Below is a draft blog post explaining the current availability, system requirements, and why "portable" versions from third-party sites should be handled with caution. microsoft+sharepoint+designer+2010+64bit+portable
Because the 64-bit architecture requires specific system DLLs, a crudely packaged portable version will frequently crash, corrupt your site data, or fail to authenticate with your SharePoint server. broken site templates