This sounds correct, Julian.
On the same Time Capsule I have a Time Machine folder for my MacBook and Time Machine folder for my wife's MacBook, but nothing else. 

The TM for my MacBook is updated regularly per day; why so, I  can't justify, but it is there so I might as well use it. "TimeMachineEditor" is a useful app for changing the frequency of updates - by hours, days, etc.

As well, on a separate 1TB FireWire HD, there are four partitions, one of which holds a sort-of part-time reserve Time Machine folder. More importantly, one other partition is used solely for a bootable Super Duper! backup done weekly.

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Best Wishes from
   Brian Ferguson.
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Model Name:	MacBook
  Model Identifier:	MacBook4,1
  Processor Name:	Intel Core 2 Duo
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  OS X 10.6.4 Snow Leopard
  Nisus Writer Pro 1.4.1
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On 20/09/2010, at 2:17 PM, Julian Gomez wrote:

> On Sep 18, 2010, at 22:11 , Geoffrey Heard wrote:
> 
>> Hi all
>> 
>> I can't find any instructions for Time Machine. The first thing it wants to do, apparently, is to take total control of the HD I want to use for back-ups. Is this normal? Can't it use just part of the HD?
> 
> My experience is that Time Machine shares the HD. I have a bunch of folders on my backup HD, and Time Machine stores all of its stuff in its own folder alongside.