Leaking Memory Check?

Can anyone recommend an easy way of checking which is/are the major culprit(s) in not returning memory to the system, or are generally leaking memory badly? My system has started locking up, despite 1 gig of RAM.

I'm not getting 'low memory' warnings.

I'm running Win XP Pro SP2 on an HP Compaq nx5000, Intel Pentium M 1.50 ghz laptop with a 40gb hard drive with 43% free space and Windows-managed virtual memeory.

 

Ok - I think I found the culprit from Task Manager. Not only is Skype (in the taskbar) using a hell of a lot of memory these days - around the 40k mark, sometimes more - but there is something called Skypepm.exe - which manages Skype plugins, which I don't need and I've now disabled, using an additional 20k plus.

And, presumably, (though this may no longer be true!!) Firefox is still leaking memory like there is no tomorrow...