Data files are stored on the PDA in a binary format with a .bdf extension. When they are transferred during the hot sync process, PConnectCE converts them to comma-separated ASCII. The collected data files must be saved in the My Documents folder on the PDA; if not, the conversion process does not take place. The files are transferred to the PC in their original format with a .bdf extension.
Try copying the BDF file back to the PDA in the My Documents folder. Then perform the hot sync again. If the file has not been corrupted in the copying process, PConnectCE should find it in the appropriate directory during the next hot sync and perform the conversion.
The files are also transferred in their original format if a process other than PConnectCE transfers the file before PConnectCE is able to transfer it. To resolve this issue, disable any other processes in ActiveSync/Windows Mobile Device Center that may be transferring the file. After resolving the issue, try copying the BDF file back to the PDA in the My Documents folder, and perform the hot sync again.