Value: 1 12.5% of free space, default
Value: 2 25% of free space
Value: 3 37.5% of free space
Value: 4 50% of free space
There is a new generation of defraggers that can work with the MFT and paging files. According to Microsoft, it is vitally important performance-wise to defragment the MFT and paging files. However, it is only safe to do so using boot-time defragmentation. Any "online" method bypasses the defragmentation APIs within Windows NT which Microsoft has provided for safe defragmentation, and can result in loss of data, data corruption, system crashes, or even loss of entire volumes.
Diskeeper and PerfectDisk 2000 and O&O Defrag DO NOT defragment these files online, but uses Microsoft's approved boot-time method.
Sysinternal's Page Defrag also defrags registry hives, event log files, and hibernation files.
If you know of other defraggers that use Microsoft's approved method, let me know.