Hard Drive Partition Help

Well my new computer should be ready in the next couple of days, and I've been reading up on hard drive partitions.

I'm not looking into this to stay more organized (I stay organized fine with one :P), or to boot multiple operating systems.

I was reading some of the advantages of partitioning and there was something about installing my operating system and stuff onto one drive, then I guess use the remaining HD space for just normal stuff.

The reason I'm looking into this is that I'm using Windows XP right now, but if I did want to upgrade to Vista later on, wouldn't this make the process much easier, as I wouldn't have to lose all my files.

Could anyone tell me if they do this? If you could please provide details as in what exactly you use each drive for, that would be great, and give me the advantages over one hunk of drive :P

Ill have a 500gb HD btw.

I just want to make it easy in case I install a new operating system later.

What I read online was to use one of the drives to store "Operating system and apps"

What does it mean by apps? All applications, or just stuff crucial to running the computer?

If someone could elaborate Id appreciate it. :)

I have a Gparted (free!) bootable cd that I have used countless times. I always include at least 2 partitions on my hard drive. If for no other reason than to prevent fragmentation of my music/video/stored games. For some reason, for me, it's only the files on the system partition that ever fragment.

On a non-gaming computer, I typically won't include more than 15gb for the operating system. I use the rest of the space to partition out for music and other files.