It should be possible to do so.
Just install your win 2000 first, without using all of your 40 gb hdd. Partition Magic works best here. Just install Win2k normally, use partition magic to resize your W2k partition (Let's say to 20gb).
After you are happy with it, then you install your Solaris 8 normally. Solaris 8 will detect the partition that is not used, and installs into it; simply because it cannot touch the ntfs partition.
Further to my previous thread, actually you do not need a boot commander or something. SOlaris comes with this little Primary Boot Menu, not pretty, but gets the job done.
So if you are installing on a system withn an existing OS, the PBoot thingy will pick all these up into a little menu, allowing you to choose between OS. It's not the prettiest thing, but works ok.