A major OS upgrade such as from 2000 to 2003 will cause SFW to be disabled / overwritten by Windows and will be reverted back to using LDM. Once this occurs, there's really no other way than to reinstall SFW from scratch after uninstall. So I recommend you to uninstall SFW first, then upgrade the OS, then reinstall SFW. (This is fine on a Microsoft cluster and hence makes it quite simple. But if it's a Veritas cluster, there are few more things to do such as backing up the main.cf file. (also back up llttab.txt and llthost.txt file) These three files will make it muxh easier to recreate the cluster that you had before after reinstalling SFW)
If you are using Veritas DMP multipathing, make sure to disable all but 1 path to the disk (Via device manager or at switch / SAN level) or pull ou tthe fibre cables to make sure no SAN disks are being accessed during the upgrade process.