This version works on Windows Vista (x64).  There are a couple of things you'll need to make sure of though:

• After installing XBF, browse to the (default install folder, modify accordingly) C:\Program Files (x86)\XboxFriends.com folder.  In here you'll see the XboxFriends folder.  Right click on it and select Properties.  In the properties dialog, select the Security tab.  Click on the Edit button.  Say yes to the UAC prompt.  Scroll down in the upper list and select "Users".  In the lower list, check the Full Control Allow checkbox (which will automatically select all of the other checkboxes) and click the OK button.  This will allow XboxFriends to automatically update whenever a new version is available.  This is also true for the 32-bit version of Windows Vista.
• Launch the 32-bit version of IE and browse to the Xbox.com website.  Make sure you have the Flash Player add-in installed.

This version also includes a few minor improvements for those running Windows XP (mostly visual).

Enjoy!