why does the installer change the partition table?

[Thufir]

No matter what options I select, I get something like:

Language: English
 Keyboard layout: USA
 Name: piter
 Login name: piter
 Location: America/Vancouver
 Migration Assistant:
 Ubuntu 8.04.1 (8.04) (/dev/sda1):
 brigitte: Mozilla Firefox

If you continue, the changes listed below will be written to the disks.
Otherwise, you will be able to make further changes manually.

WARNING: This will destroy all data on any partitions you have removed as
well as on the partitions that are going to be formatted.

The partition tables of the following devices are changed:
 SCSI1 (0,0,0) (sda)
 SCSI1 (0,1,0) (sdb)

The following partitions are going to be formatted:
 partition #5 of SCSI1 (0,0,0) (sda) as swap
 partition #5 of SCSI1 (0,1,0) (sdb) as swap

which concern me because I don't want to lose data on sda but don't want 
to back up (lotsa cd burning) at the moment.

I tried the manual approach, selected which sdb partitions I wanted 
effected, but keep getting that message that the partition table for sda 
has been changed.  If so, I didn't intentionally change it :( 

The specific concern is that the partition table was changed, causing 
data loss.  I never changed the partition table for *either* drive from 
the GUI installer.

Opting for the manual approach I ensured that only sdb was selected and 
didn't select to have the installer format anything.  So, I'm curious 
about the above message.

Per <http://groups.google.com/group/ubuntu-users-archive/
msg/52e5cbd17f02d4d0?dmode=source> I would like to seek a few opinions 
before proceeding.  (I'm not terribly inclined to proceed with a non-GUI 
install at this point, just would like to solicit more thoughts as to how 
to interpret the above message.)




thanks,

Thufir