I don't have a PC to test this on at the moment, but try this on for size
First, I'd recommend a text based variable, rather than the number 1
set var=0
set /p var=Enter your User Name:
goto DEL

EL
deltree /y C:\Documents and Settings\%var%\Cookies\*.*
I'll find out specifically for you tomorrow at work, when I'm back at my PC.