Android adb shell delete SQLite database

I need to delete an SQLite database and in order to do so , i need to access adb shell.

i'm on windows 7 and i have my sdk installed on:

C:\Users\Omar\AppData\Local\Android

i have opened the cmd and typed adb shell but with no success here is my output :

C:\Users\Omar>adb shell
'adb' n'est pas reconnu en tant que commande interne
ou externe, un programme exécutable ou un fichier de commandes.

c:\>adb shell
'adb' n'est pas reconnu en tant que commande interne
ou externe, un programme exécutable ou un fichier de commandes.

"unknown command"

Do i need to do something before calling the adb from my windows cmd ? like creating a classpath ?

Thanks a lot in advance ^^