What you can use is the Client Side Caching feature - this is definately part of XPPro, not sure about XPHome.
1 - get the file on the non-laptop to the state you want it, and delete the one on the laptop
2 -On your laptop, select the .pst file (or whatever it is you use to save the mail gubbins) on the other system , right click it, and select 'Make Available Offline'. If the option isn't there, control panel/folder options/Offline files/Enable Offline files, & enable the times you want to sync when the machines are connected.
You are always going to have a problem with this method if you download mails on both systems without syncing between downloads
hth