How to make back visible extensions in directories?

Yes I agree with you BillDl.
It could be  in windows explorer since >>all folders the name of which contains a dot, everything after the dot (and the dot itself) do not display, >>.git folders!
Since this folder directory is created by Git
is Git capable of recreating a new directory? or associating these folders again? We don't windows explorer folders to get messed up.
 See what's inside your .git directory and below that is a list of references for your level of expertise.
http://gitready.com/advanced/2009/03/23/whats-inside-your-git-directory.html
Git In Five Minutes
http://classic.scottr.org/presentations/git-in-5-minutes/
Finding the path where Git is installed on a Windows system
http://stackoverflow.com/questions/8507368/finding-the-path-where-git-is-installed-on-a-windows-system
Git installer Read Me
http://git-extensions-documentation.readthedocs.org/en/latest/getting_started.html
Looking at the list of choices for registry keys Mahesh linked maybe this one>
Directory            Directory protocol associations
http://www.eightforums.com/tutorials/8486-default-file-associations-restore-windows-8-a.html

Thx all for your suggestions.
I'm trying to keep possibly dangerous solutions at the bottom of my list.
- @Lionel: this is the safest, so I started here. Does work partially: now, only the "extension part" of folders names (ie, what is after the last dot) is hidden, while I think I remember that previously the folder names were hidden after the first dot.
- @Merete: I forgot to take a backup, while I'm usually slightly on the paranoid side. System restore is on my list, but currently at the bottom.
- @Mahesh: good link. I will review the changes they propose for folders
- @Bill: what I did was stupid... but of course did not look such for me at the time! Let me enumarate some of my errors to describe the process which led me here
  = I had downloaded emule from an apparently safe source, but in fact this installed lots of additional crap instead (Priceless, HQVu, "googleupdate.exe" (more precisely something similar) and some others I don't even remember the name,).
 = I uninstalled everything I could thru regular windows uninstall and ccleaner for those I could not... but this left lots of programs, browsers add-ins etc
 = I killed in \programs, programdata and appsdata eveything that seemed related (using folders creation date as the main criteria)
 = I then used ccleaner to clean deleted files, remove browsers add-ins, and checked the registry, wiped everything clearly related
 = then forgetting it was late B-( I decided to clean the registry base (and, of course, forgot the elementary precaution to make a backup). Looked for all occurrences of "googleupdate.exe" (which is not! google\update.exe)... but probably deleted too aggressively elements which contained that). Did the same for "priceless".

Just for now, everything looks fine, except that I probably deleted the keys that defined what to display for folders

- @Merete2: only the folder name is not visible in Windows explorer, but the folder is visible! So I can access its content, and using git is not a problem (the folder is here, whether I see or not its name). The trouble is greater when looking at a directory which holds several .dotted directories: I can check the names with the dos box, but if I want to select a folder with windows explorer it is slightly more difficult (but possible)

To illustrate the problem, look below at the attached screen captures: the same directory in windows explorer and a dosbox. Note that all directories names are displayed "up to the last dot"
Dos Box:

B-) Problem in fact solved using Lionel's suggestion.
- I had launched Windows Explorer, changed options for folders display: the result was the one displayed in the screen capture above.
- I launched another instance of Windows Explorer, and now everything is back to normal.

So the solution would be
- open windows explorer, make folders extensions and system folders invisible, close
- reboot
- open windows explorer, restore folders extensions ans system folders visibility as wanted
- close windows explorer
- open windows explorer, all should be OK now.

Thx all for your highly valuable contributions.

I've requested that this question be closed as follows:

Accepted answer: 350 points for lionelmm's comment #a40463768
Assisted answer: 50 points for Merete's comment #a40463783
Assisted answer: 50 points for Mahesh's comment #a40463795
Assisted answer: 50 points for BillDL's comment #a40463924
Assisted answer: 0 points for fibo's comment #a40464183

for the following reason:

Lionel gets the most points, since his solution was riskless and the first.
Contribution by Merete, Mahesh and Bill are worthwhile also, and should be coonsidered in cases where Lionel's solution does not work

Excellent news fibo.  I'm glad you got this fixed.

glad to help--did you request the question be closed or did you accept my suggestion as a solution--it looks like you requested a close--please verify--thank you and good luck

questioner may have mistakenly requested a close instead of an acceptance--see the closing comment

Lionel,
Not sur I'm "accepting" now: I have followed the same steps as before, and they match to the RTFM for multiple comments.
The only point that is different is that previously I had also selected my comment (with 0 points) as part of the solution since it summarized the complete solution.
I am not now.
If things stay the same... let's keep the things going, eveything will get fine within 3 days, let's spend time somewhere else

Thank you fibo

Fibo thank you from me too glad I could help :)