Vista partition may disappear

If you are planning to dual boot XP and Vista, keep in mind that you format
the partion on which Vista to be installed using Vista. Dont format the
partition using XP and then install Vista on it. Else Vista partition may
disappear.

Check this KB article:
http://support.microsoft.com/?kbid=931854
SYMPTOMS
If you use Microsoft Windows XP to create a new partition on a computer that
has both Windows XP and Windows Vista installed, the partition that hosts
Windows Vista may disappear.
CAUSE
This problem may be caused by a error in Logical Disk Manager. If the
partition that hosts Windows Vista was created during the installation of
Windows Vista, a 1-megabyte (MB) alignment boundary is created on the
partition. This alignment boundary differs from the alignment boundary that
is created by Windows XP. Therefore, when you use Windows XP to create a new
partition, the different alignments may cause this problem.

WORKAROUND
To work around this problem, do not use Windows XP to create a partition on
a computer that also has Windows Vista installed.