How to make hidden files unhidden (normal) again?

Remove the period from the beginning of the folder name. Mac OS does not respect Win "hidden" flags after you move them over.

To toggle invisible files type this into the terminal.app:

defaults write com.apple.finder AppleShowAllFiles -bool TRUE
Press return, then type:
killall Finder

Change TRUE to FALSE when you want to hide them again.

If it is indeed an directory it should not be hidden unless there is a period in front of the name. Maybe you have an exception. Where is it located? When you do a ls -al on the current directory is there a d at the starting permission string like this:

-rw------- 1 who staff 642 Feb 2 2010 .viminfo (Hidden text file)
drwx------ 3 who staff 102 May 21 13:40 Applications (Normal root directory)

Better yet run "ls -al" on the directory and post it.

The fact that it is hidden in Win has no bearing when you move it to OS X. Your Mac does not respect Win file system. As it should be:) If you have any familiarity with Unix/ Linux that is pretty much the backbone of OS X. Maybe this helps maybe not. Welcome and good luck.

Open Terminal.app.
Navigate to the Directory your file resides in. Typing:
cd /The/Location/of/your/directory or just:
cd "space" - Drag your folder to the Terminal window and it will write out the location.
Press return.
Then type at prompt:
ls -al
Cut and paste the output.

How about creating a new folder and dragging the contents into it with hidden folders turned on? Then toggle hidden folders again as described above.

Is the folder in the above ls output? In what method can you see the folder?

So you can use the false command, create a new folder, open the "hidden" folder and drag it's contents to the non hidden new folder you just created and it will stay visible.