For a new machine (which is meant to be dual-boot), it may be better to install Linux first, since the partitioning information can be got right-first-time…
If Vista is Installed First
However, once Vista is installed, space must be made for Linux (and the shared partition).
Shrinking the Vista partition is fairly easy using the Vista tool included [...]

For a dual-boot machine (where the main desktop would be Linux), a common ‘data’ partition makes sense (rather than allowing root access by Linux to the Vista install, or visa-versa).
Shared Partition
Since the Vista driver requires it, you need to format the shared ‘ext3′ partition with : /sbin/mkfs.ext3 -I 128 /dev/sdA
Partitioning Problems
The Vista driver seems to [...]