Change linux distrabution on first primary partition from opensuse to ubuntu?
 

I have opensuse running as the primary operating system on my HD. I installed it when I first got this computer, and use it really really infrequently, after all I only have 50GB of hard drive space partitioned off for it... But then on the remaining space I have a windows system operating.

Basically, I dont want opensuse there, I want Ubuntu. Now I have been experimental when it comes to tearing down the OS and re-installing a new one, I even tried various flavors of linux in the first place, but secondly, I don't want to loose my windows system at all, after all it has 100GB of hard drive space dedicated to it ( this is something I spent a lot of time re-organising when I upgraded to 7 ) and plenty of time doing cool stuff on...

The question is really if I delete and re-install a new OS on my primary partition, such as Ubuntu, then am I going to loose all my time and energy that I poured into the windows, because linux will decide I need a new boot order and forget that windows exists. Like Grub might tear away the fact that windows exists?

Believe me when I say that it might happen considering grub did this once when I used this same setup earlier with XP and openSUSE, and grub just couldnt find XP?

So, HOW do I make sure that if I go ahead and get Ubuntu and load it, its going to keep the way windows is running smoothly? I know backing up is an option if anything goes wrong, but 'sigh' I'm not going to switch it back if that is the only option... What are my options?

Grub USUALLY does a good job at finding other OS partitions and setting them up for you. However, unless something has changed in Windows 7, it will not boot from the secondary IDE.. for this I suggest adding the following to your /boot/grub/menu.lst

My suggestion is to back up your Windows installation, since that's what
you consider the most valuable.

Do not remove the opensuse installation. All you need to do is install
Ubuntu using the same partition(s) that opensuse uses. This will completely
erase opensuse and will not touch the Windows partition. During the setup
you will be able to choose whether to boot Ubuntu or Windows by default.

@carltm

I'm not so certain, and therefore I want to avoid trying it. It has happened before that it was totally glossed over by grub and the whole 100GB space missed completely ( XP and everything )!

I'd just have to tell you to be careful what you click on during the installation. "User-friendly" distros like Ubuntu have streamlined installations that make some assumptions, so you have to make sure that you configure the partitions yourself, and explicitly instruct Ubuntu to install on the partition previously used for OpenSUSE. It's possible that if you don't specify it will assume you want to format and replace everything on the harddrive. From my experience it will always give you a screen for partition options during a Ubuntu install, but just read everything carefully before clicking "next".

partioning
 

On the face of it bret's answer should be taken note of but also be aware of the assumptions made by the 'easy to use'. Going manual involves taking note of cylinder numbers and matching them exactly, so perhaps do a printout of fdisk -l and or df -h beforehand.

Fred.