Firefox is a web browser and doesn't handle your emails. Not sure what exactly 'i reset the firefox once' means, but it would not impact Thunderbird.

What you did with Thunderbird is a different story.

my computer was running slow so i delete the temp files from my computer , i did only three steps:

1- ) delete temp ,%temp%

2 - ) ran del tmp *./s in cmd before that cd.. , cd.. change the directory twice to go to the c :

3 - ) refresh the firefox and reset the chrome

4 - ) restart the computer

after that i checked in my thunderbird mail all the folders that i had got deleted ...

so please tell me where did i made the mistake due to which i lost my thunderbird folders....

Normally, Firefox and Thunderbird store their important data completely separately. Assuming you did not do a custom installation, a Firefox Refresh should not touch Thunderbird files. Anyway, it's easy to check: a Firefox Refresh moves your Firefox profile folder to the desktop inside an Old Firefox Data folder. If you look inside that folder, do you see anything related to Thunderbird?

Regarding your #1 and #2, I don't know exactly what those commands do and I'm not about to test it for myself. ;-)

1 ) Running del %temp% delete all in ......\appdata\local\temp That doesnt make no harm BUT 2 ) Running del tmp *./s would find tmp but also *. files. Files without an ext. Just what your thunderbird mboxes are.

Try it with dir tmp *./s and you see what a damage it does