Before you begin make sure you have a recent back-up of your wallet.dat file.
Also make sure your FeatherCoin client is not running.
Step 1:
Download the latest FeatherCoin client from the website (http://www.feathercoin.com).
Step 2:
Extract the files to (for example) your desktop.
Step 3:
Open explorer and browse to your active FeatherCoin wallet location. (i.e. C:\Program Files (x86)\FeatherCoin).
Step 4:
Copy the extracted files from you desktop and paste them in the active FeatherCoin directory (select ‘Yes’ if being asked to overwrite existing files).
Step 5:
Double click the Feathercoin-qt.exe file and you are done!