Two Different Installation Types?

We've got 2 installations of Parallels Desktop on our MacBook Pro machines:

1. On machine ONE, there's an "ISHTAR.pvm" file plus an ISHTAR folder which contains a "config.pvs" and "harddisk.hdd" file. The "harddisk.hdd" file is about the size of the PC hard disk, but the "pvm" file is relatively small.

2. On machine TWO, there an "ASTARTE.pvm" and nothing else that I can see. The "ASTARTE.pvm" file is about the size of the PC hard disk.

QUESTION: Why does machine ONE have more files, including an "hdd" file, whereas machine TWO has one? Is one setup better than the other; I did identical (I thought) installations on both machines.

Thanks in advance for shedding some light on this for me!

- Keith