My slave 200G HDD changed from NTFS into RAW after restart, and I seem to have lost everything that was on it! Is there any way it can be changed back to NTFS without losing any data?

Is it showing up as a drive in windows disk management? Any data recovery software should restore a lost partition with all data intact as long as the drive isn't damaged and you haven't over written the data.

You might try this one: http://www.cgsecurity.org/wiki/Main_Page

A corrupt or missing boot sector will cause such kind of problem.

To fix the boot sector, you may refer to How to Fix the Boot Sector Problem?

If it still cannot be solved, you have to recover all the data out and then format the partition as the system indicates so that you can enter the partition again.

How to Recover Data from Raw Hard Drive?

After you have copies the data out, you may format the partition to NTFS.