First, regardless of method used, it is strongly advised to backup openSUSE, at the very minimum your /home directory. You are working with different partitioning tools, and in particular, you are touching the partition table with both Linux and Windows software, which handle the table differently. Windows is exceptionally rigid, unforgiving, and doesn’t tell you what’s it’s doing. And even if you use other tools like SuSE or GParted to partition, you will still be writing to the table with XP when it installs. Best also to have Windows reformat the partition, which you have to do anyway if using NTFS. Having said that . . .
If you are going to do a clean install of Windows, you don’t need to do any advance partitioning. The Windows installer will do it for you. You cannot resize, but you can delete what it sees as the C:\ partition, and then re-create a smaller one.
Next, as already mentioned, Windows is going to install its own MBR, like it or not. Let me suggest that before doing any of this, you go into the YaST Boot Loader module and install grub to the “root partition”. In the event something goes awry, this can come in handy getting yourself back working.
You can reinstall grub to the MBR with the Repair menu option on your openSUSE install DVD (can also be done from Rescue, but that’s using the command line and grub shell as opposed to Repair which will use YaST).
Finally, and this is important: With the first partition downsized, you will have unallocated space between the first and second partitions. When you add a new partition(s) in that space, it will change the partition sequencing. Right now, SuSE is on sda2. If you do the above, reinstall grub in the MBR, go into SuSE to add new partition(s), and then reboot - it won’t work. This is because when you install grub in the MBR, you place a pointer to the SuSE boot partition. It will be sda2. Except now with the added partition(s), SuSE is no longer on sda2, it’s sda3 (or sda4, if you added 2 partitions). And your grub device.map file (which tells grub which partitions correspond to its hd0, hd1, etc.) will also be wrong. So you need to add the partition(s) in the used space before reinstalling grub in the MBR, or, reinstall grub once again to the MBR after having made the partitions.
You may have another consideration, depending on the size of that space and size of the drive overall. If this is a smaller drive, this won’t apply. But if one of the new large drives, it very well may . . . If you add 2 partitions in that space, you will have 4 primary partitions; you cannot add any more. The method by which more than 4 partitions is implemented is for one of the 4 primaries to be an “extended” partition inside of which “logical” partitions can be created. It is vastly preferable to have that extended partition be the 4th. The 2nd or 3rd can be used for this purpose, but it creates complications. So it may be best to only create 1 partition in that space, leaving an unused 4th (for now) for a later extended partition, should you later want it (e.g., to create a separate /home).
