As far as I know there is only a decent plugin for Windows that makes it possible to read ext2/ext3 partitions. If your partitions are reiserfs format or other that no luck there.
If you want to restore the Linux boot you should be able to boot with the install CD (asuming you have openSUSE 11.0).
Basically boot the CD/DVD and choose the ’ Repair Installed System '. At the next choice screen select ‘Expert Tools’. You should then get the option to install the bootloader again. Choose that and select the openSUSE boot partition.
After having done this you should be able to boot back into your Linux part and can add the XP boot to the grub menu.
If it’s only data you want to copy off the Linux partitions… maybe easiest download it and boot with a LiveCD. Once booted you can copy the relevant files from the Linux partition to your Windows partition. Saves you any hassle you might run into getting access from within Windows.
If you are using opensuse 11, it automatically sets inode to 256 instead of 128 (i think this is what it was on all versions before 11). If you are using the tool im thinking of for windows (ext2fs i think?) then it wont read 256 inode partitions.