Solution
.TDM and .TDX files are a pair. Both are required to be opened the files successfully. A .TDM file can be created through LabVIEW, LabWindows™/CVI™, Measurement Studio, SignalExpress, and DIAdem. A .TDM file automatically creates a .TDX file with an identical name. If either the .TDM or .TDX is missing, the error will appear as seen in Figures 1 and 2.

Figure 1
. DIAdem TDM load error

Figure 2
. Excel TDM load error
The meta data is saved in XML format in a .TDM file. The bulk data are saved in a compact binary form in a .TDX file. If either file is lost, the other file is not recoverable programmatically. It is possible to manually create a .TDM file. However this requires strong knowledge in the binary construction of .TDM files. For more information about this format, refer to this page .