I think that if the RAID5 volume is on a set of disks considered a dynamic disk, the information you need is stored in the LDM (Logical Disk Manager) database. I think that as long as you don't reformat your system partition, erasing the boot sector, you will probably be able to bring your RAID5 online without problems, once you've loaded any needed SCSI drivers. I'm not sure how you'd back up the LDM database if you were going to reformat the system disk.
But let's say you didn't back up the LDM. Let's do the following:
1) Take the disks that are part of the RAID5 array physically out of the system.
2) Reformat and rebuild your server, and install service packs. Don't install applications yet. Turn the server off.
3) Add the removed disks back to the system (this may just involve plugging the SCSI cable back in.
4) Boot the server up again, and go to the Disk Management console. You will see some drives in there listed as 'Foreign'. Make sure the number of disks listed there is the same as in your RAID5 array.
5) Right click on the 'Foreign' disks and choose 'Import Foreign Disks' from the context menu.
6) Click Ok, then choose 'Verify Volumes on Foreign Disks.
7) Acknowledge 'Data Incomplete' warnings, if any. Continue clicking OK when needed and the LDM will bring the disks into the system and initialize the file system.
8) Right-click each new drive and 'Reactivate Disk' till all the drives have been reactivated. Plan on waiting a LONG time for the volume to be brought back on line.
ShackDaddy