I have had zero problems with the partition resizer that comes on the Suse 9.1 personal CD, which you can download the ISO for.
I've taken brand new XP laptops of co-workers, dropped the CD in, and it automatically resizes the XP partition for you flawlessly, set up dual booting, and then installs Suse Linux for you, all more or less just by clicking "OK" a few times.
It might be easiest just to get a copy of the suse 9.1 CD... do this... and then once it is all set up just trying to install Slackware (I'm assuming it's slackware you want) on top of whatever partitions Suse creates...
Vince
