Both iCloud and GMail sync notes with a folder on their email servers. There is no way (that I know of) to make them sync with an actual note application on the computer.
From the sounds of things OS X Mountain Lion is going to change this around a bit, since it will add a Notes app to the Mac that will sync to iCloud and iOS devices. I'm not sure how they are going to do that, so I don't know if it will also create a new syncing option on Windows machines.
If it does happen it will probably require an update to iOS 5 and the iCloud control panel on Windows, or we may have to wait even longer for iOS 6.
Now, it is just barely possible there is an app for Windows that will create/edit and manage notes in using the notes folder in your GMail and/or iCloud account; but I've never looked for one.