Folder that acts like a file

I have a pc- user (windows 7 os) trying to access a folder on my mac server. However, the folder on my server is registered a "file" type. When the pc-user double-clicks on the folder "file", it would ask what type of program to run the file on. I have no problem accessing the same folder from my imac. What should I do?

Thanks in advance.

*bump*

I have never heard of a folder being viewed as a file on another operating system. Are you sure the folder is not security-locked, for instance? And how do you go about connecting your PC and Mac? Also what extension (.***) does your Windows read the folder/file?