[megaloman]

Код:

@Echo Off
cls
	Set "BoxIn=C:\Users"
	Set "Box2=AppData"
	Set "DelFile=*.txt"

	FOR /F "usebackq delims=" %%u IN (`Dir /A:D /B "%BoxIn%"`) DO (
		If Exist "%BoxIn%\%%u\%Box2%" (
			Echo === "%BoxIn%\%%u\%DelFile%" 
			Dir /B /A:-D "%BoxIn%\%%u\%DelFile%"
		)
	)
Pause
GoTo :Eof

Для боевой работы замените Dir /B /A:-D на Del