I believe that what you are possibly referring to isn't the resizing of the $MFT but a reduction in the size of the MFT Reserved Zone. As I mentioned earlier, it is currently not possible for ANYONE to reduce the size of the $MFT. The only way that this can be done is to backup the data, reformat the drive and then restore the data. However, the size of the MFT Reserved Zone certainly can change (the MFT Reserved Zone is represented with Diskeeper by the white with green slashes through it).
When an NTFS partitions is first formatted, it creates the MFT and remainder of the metadata ($Logfile, $Bitmap, $Upcase, etc...). It also creates the MFT Reserved Zone. Depending on which operating system is in use, the MFT is created according to the following:
NT4 - Fixed Size of 12.5% of the partition.
Win2k/WinXP - Dynamically created everytime the partition is mounted and goes from the first record of the $MFT to the first non-free cluster - up to a default max of 12.5% of the partition.
Under NT4 and Win2k, the free space contained inside of the MFT Reserved Zone can NOT be used by defragmenters. Under WinXP, it can.
Under Win2k/WinXP, as soon as the file system puts a file in the Reserved Zone and the partition is remounted (System rebooted), the size of the MFT can shrink from the 12.5% default to something smaller. I believe that this is what you are seeing.
Was this a clean install/format of the NTFS file system under WinXP? If so, then the $MFT should be placed roughly 1/3 of the way into the partition. That is where the file system itself creates it on a clean format - results in a 5-10% performance improvement with the NTFS file system. By placing the MFT at the beginning of the drive, your defragmenter has "robbed you" of this additional performance benefit.
If this was a conversion to WinXP from a previous version of Windows, the $MFT was originally created at the beginning of the drive and your defragmenter has still "robbed you" of this additional performance benefit by not placing the $MFT further into the partition.
- Greg/Raxco Software