Yeah, the
bluetooth.btwsendto file is an instruction set which, i guess, had been corrupted and reinstalling the software doesn't repair it
.
But luckily i found a file name
btsendto_explorer.exe in the bluetooth installation directory which do not run if double clicked but experimented its shortcut in the
shell:sendto folder which is working the same as the instruction set used to work.
Thanks for the hint.