Hello vseenu, you may already be well aware of what I'm about to convey regarding dual-booting.
I imagine that when you install Microsoft Windows XP successfully that it will overwrite the MBR -Master Boot Record-. Many people have the inverse situation that you do where Windows XP came preinstalled and they would like to add GNU/Linux. For those people Linux has boot loaders that, when overwriting the MBR themselves, often find Windows XP and make provisions for it booting too.
Windows XP makes no such provisions for
finding other operating systems and as a result could leave you unable to boot SUSE and Ubuntu. Consider the use of the powerful, and potentially destructive if misused,
DD command as demonstrated by jiml8 in the thread
Help on potential loss of the MBR by an OS re-install. For additional reading I suggest running a search here at Linux Questions for the following phrase and keep the quotation marks.
On a different note, It could be I'm misreading your wishes, your needs or your partition setup. However, if you have a 320 GB hard disk drive with just two distributions on it and only 40 GB left, unless you need that much space dedicated to those two partitions, then now might be a good time to restructure your partitions around the modest needs of those distributions and not the ample hard disk drive space alloted. This is merely a suggestion however, your configuration is entirely up to you of course. The output of
fdisk -l may prove useful to your thoughts on the subject.
Consider the
OpenSUSE system requirements and the
Ubuntu system requirements.
