In Windows debug.keystore file is localtes at C:\Users\%Username%\.android folder. This file is created when you install your android SDK and is valid only for a year. After this perod you will start getting this error Error getting final archive: Debug certificate expired on xx/xx/xxxx.
To remove this error simply delete the file and run the program again. In my Eclipse I have enabled Project->Build Automatically so it directly worked but in case you have disabled it you will need to clean the project Project->Clean.. select your project and press ok. Then you will need to build it manually. 3rd click on your project and select Build project.(Note - You will only see this option if you have diabled Build Automatically feature in your Projects Menu)