The memory details suggest that virtual memory is not a problem and the system isn't resorting to the swap file to complete the task. Although if you ballpark resources used by the major process:
OS: 250 MB minimum or more for XP, probably closer to 350 MB
Studio: 75-150MB or more depending on open editors and objects in the tree.
Server: anywhere from 45 MB starting to 150+ MB depending on what is cached. I have seen a server run and maintain over 500 MB of memory because things are cached and not freed up.
MySQL: No experience with running my own machine. I'm guessing anywhere from 25MB to 100MB
Apache: 20MB
PHP FCGI agents: 4 @15MB+
As you start to add this up at peak times there may not be enough memory and hence the system will hit the swap file. On a laptop harddrives are generally slower so this would really slow things down.
There is also the possibility it is MySQL:
http://bugs.mysql.com/bug.php?id=17984
Partway down on that thread they talk about MySQL beign slow on XP, even with an Inel processor. What build of MySQL are you using?
Dave