TransformsAtSource Policy
If this per-user system policy is set to "1"; the installer searches for transform files in the root of any network sources in the source list for the product. By default, transforms are stored in the Application Data folder of a user's profile.
Windows Installer interprets the TransformsAtSource policy to be the same as the TransformsSecure policy.
HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\Installer
REG_SZ