TortoiseCVS

TortoiseCVS is a graphical CVS client for Windows. For more on using this with Drupal, see http://drupal.org/node/227524

Step 1: Checkout Drupal from CVS

1. Download and install TortoiseCVS.
2. Right-click anywhere, Checkout from CVS...
3. Fill out the following settings:
   
4. By default, Drupal HEAD is retrieved. If required, click the Revision tab, Choose branch or tag and select an older version, e.g. DRUPAL-5.
5. Click OK.
6. If prompted, enter the password 'anonymous'.

Step 2: Creating a patch

1. Make whatever changes to the Drupal files.
2. Right-click the "root" Drupal folder (e.g. "drupal"), CVS > Make Patch....
3. Enter a name, Save.