I read a walk through in the British magazine PC PRO
PC PRO: IT News & Reviews about transfering an old computer XP based system on to a new computer running Vista, with the XP becoming a guest to the Vista host, using the product available at
VMware Converter for workstation to virtual pc and virtual machine migration - VMware. and then operating the installed client through VMware server Console. [ I haven't tried to this myself but a few points for you if you want to, when you load up the VMware converter in your old machine you will get a message asking have you an enterprise licence, respond by clicking "continue in starter mode", the transfer software should be available gratis at the www address above, the utility to run the installed client is called VMware server
VMware Server, Virtual Server Consolidation, Free Virtualization - VMware and should be available gratis ( dont worry about the "server " bit in the name that will not cause a problem runing on Vista, but remember once your guest (s) is/are installed as this is designed as a server application shutting down the console will not shut down any guest(s) you have running, you need to shut down any guest(s) before you exit the console ).
Best and Warm Regards
Adrian Wainer