Files whose filenames begin with a period (for example, ".filename") are normally invisible in Mac OS X. However, if you share disks between a Mac and a Windows-compatible computer, you can see the files. They should not be deleted.
Note: This document applies to Mac OS X 10.0 through 10.3.9.
Symptom
Files whose filenames begin with a period "." appear on the disk when viewed with a Windows-compatible computer.
This can occur when you use writable, portable media with both a Mac and a Windows-compatible computer.
Solution
The files can be safely ignored and should not be deleted.
To make the files invisible when the disk is used on a PC, you can set the "hidden" attribute for the files within the view options. Refer to the Microsoft Windows Help documentation for instructions.