To the best of my knowledge, there's no way to perform a complete copy of operating system, files and applications in the way you are hoping for - at least not without rooting and possibly access to specialised hardware. In reality, there's not much point in doing so anyway.
All you really ever need to back-up on a phone is your personal files - photo's, music etc plus "collected" data like contacts and texts. Those can be backed-up via Google's usual syncing methods or you can copy them off to your PC. You can also back-up your apps if you wish - there are free applications that can do that - such as "App backup & restore". Texts can also be backed-up using an app like "SMS backup & restore". Whether or not it's actually worth backing-up apps when you can easily download them in a few seconds is debatable - I'd say it's only worth bothering if you have no access to wi-fi - purely because of the cost of using your data limit.
One thing you can do to make life a bit easier - move as much data as possible to the SD card. That way, if you ever do need to reinstall Android, your personal files and data are not affected - plus, it's really easy to access or back-up the contents of the SD card to your PC. You can also tell the phone to store most apps onto the SD card - that will save your phone's memory as well as making it easier to restore them if necessary. There's a free application called "App2SD" (and there are others that do the same) that makes moving your apps to the SD card easier. Some such apps require rooted phone - so check that before downloading.
