If you wanted a safe way to test Suse with the option to resort back to Vista if you really really really really really MUST, you could do something like this:
Boot a LiveCD (or usb pendrivelinux disk-- anything which will give you a full blown linux with the ability to access the drives on the computer)
Plug in a USB harddrive with plenty of space (at least the size of your existing harddrive in the computer), and mount the USB drive (if it doesn’t automount). It will probably be a device such as /dev/sdb1. You can see what it is by running ‘dmesg’ and see what USB device just showed up. Mount it if necessary: # mount /dev/sdb1 /mnt
Find the device of the internal drive (ie: /dev/sda, or /dev/hda)
do:
dd if=/dev/sda of=/mnt/vistaBackup.dd bs=1024k
(assuming /mnt is the mountpoint of usb external drive)
Once complete, you should have a file: vistaBackup.dd the same size as your internal drive.
You should then be able to shutdown, and install whatever you want on the system. If you need to get back to vista, you boot that LiveCD or pendrive again and do the opposite:
dd if=/mnt/vistaBackup.dd of=/dev/sda bs=1024k
Before doing anything, make sure you know what all your devices are.