WHOA!!! Stop using that PC!! On another Puter, download this pgm, REST2514.exe onto a floppy, install it onto the same floppy [it will fit] and then insert it into ur PC with the lost stuff and run it from the floppy [to save disk file damage it does not install - that is the beauty of it.. one of em, anyway..]. http://www.snapfiles.com/download/dlrestoration.html
..it will even find stuff u did a shift-delete on. But only if you have not overwritten it!! Just going on the web causes Xp to write tons of stuff onto a disk.
are you sure the directory C:\docs&sets\your-name\Application Data\Thunderbird\profiles\xxxyyyzzz\Mail\Local Folders is gone ?
If not, then copy it to a safe place
A known problem: if an folder goes over 1Gbyte, you are in trouble; solve this using subfolders; Thunderbird implements large folders as a subdirectory + 2 files, all having the same name, but a different type
re-configure (or re-install) Thunderbird; re-configure can be done by creating a new user
now you have a new "Local Folders" directory. Now you can transfer bit by bit the directories from the safe place.
Setting the time back is a bad idea on windaz, all kinds of strange things might happen