Partitioning your drives isn't a big problem. Almost any third party software will do the job for you. Partition Magic springs to mind as it's probably the best known, but any others would do. You can choose to format each partition in any format you like that's supported.
Loading an older operating system is much more challenging. If you mean you want to operate a dual boot machine, then it would be normal to load the OLDER system first on drive C: and the NEWER system on one of the remaining partitions. The newer system would then pick up the old and offer a boot menu at start-up.
I'm not certain if maybe a boot manager like Boot Magic would serve your needs. Vista's a new animal and it's quirks have not yet been fully discovered.
The other option would be to use Vista as a base for operating a virtual server. You could then run as many virtual machines (together) as you wished of whatever flavour.