You will need to enter the product key from the bottom of your laptop (or under the battery compartment).

hello all,    i have a dell inspiron 1545 running windows vista. it started to ask me for a product key, i don't know what to do, i haven't installed any pirated software and now im stuck. i would appreciate any help i don't mind loosing all my info just need my laptop to work like normal. thank you

Hello Kayvilla,

As TheFlash1932 has said, you may use the product key from the sticker on the computer. In case you do not have the product key, you may use the Dell OEM disk (shipped with the computer) to re-install Windows. Please try the steps mentioned in the article on How to manually reinstall Windows Operating System. Post re-installation of the operating system, please ensure to install the drivers in the correct order. 

**Note: Please ensure to back up all the data from your computer before re-installing Windows as it would erase everything from your computer.

Hope this helps!