Unfortunately there are some quirks with using the gadget for Google Desktop, but some people have had success with the following:

1. At the top of the Sidebar, click 'Add'.

2. Copy and paste the following URL into the 'Search gadgets' text field:

http://www.rememberthemilk.com/services/modules/googleig/rtm.xml

3. Press the 'Search gadgets' button.

4. Press the 'Add' button next to the Remember The Milk result.

Hope this helps!

Thanks!

That worked, I managed to add RTM to Google Desktop. However, I can't log in, or rather trying to log in just opens up an Internet browser. Any workaround to this?

I think that Google Desktop uses IE's cookies, so you may need to login with IE first before this works. Hope this helps!

Thanks again, forgot to mention that I use Firefox...

Even if you use another browser you may need to login with IE initially (as that's the browser that Google Desktop uses). Once you've logged in with IE then you shouldn't need to do this again. Hope this helps.