1. Parameters registry is
   HKLM\System\CurrentControlSet\Services\RRamdisk\Parameters\
   why RRamdisk, 'cause XP SP1 contain a Ramdisk driver for XP Embeded.

2. Parameter: DiskSizeM, DiskSizeK
   your desired disk size, the unit is M bytes or K bytes. The DiskSizeK
   has higher priority.

3. Parameter: MediaType
   the reported drive type,
       1 -- RAM Drive
       2 -- Fixed Media (default)
       3 -- Removable Media
       4 -- Floppy Diskette

4. Parameter: DriveLetter
   name say it is, default is R:

5. Parameter: SectorsPerCluster 
   your desired cluster size, zero for driver pickup:
       <= 2M		FAT12, cluster=512
       <= 32M		FAT16, cluster=512
       <= 64M		FAT16, cluster=1k
       <= 128M		FAT16, cluster=2k
       <= 256M		FAT16, cluster=4k
       <= 512M		FAT32, cluster=2k
       <= 16G		FAT32, cluster=4k
       ......
   you can specify smaller cluster size, force pre-format as FAT32

6. Parameter: Image
   maintained by rdutil utlilty, mainly for preload NTFS image. eg:
   1) load ramdisk, don't write anything
   2) format the ramdisk
         FORMAT /FS:NTFS /Q /V:RamDisk /A:512 R:
   3) adjust logfile to minimum size
         CHKDSK /L:2048 R:
   4) reset access rights
         CACLS R:\ /G: BUILTIN\Adminstrators:F
   5) create necessary structure
         MKDIR R:\TEMP
   6) pack the disk image and save to registry
         rdutil R: registry

   Notes:
   1) You should leave RamDisk as clean as possible before packing,
      the max packed image size is 64K.
   2) The disk image only valid to same RamDisk size, you should
      re-create disk image when size changed.
   3) The driver internal formater will disable if this registry present,
      corrupt/size-mismatch value leave an un-formated disk.

   rdutil utlility usage:
   1) backup registry image
         rdutil save filename
   2) restore registry image
         rdutil load filename
   3) report packed image size
         rdutil R:
	 rdutil registry
	 rdutil unpacked_file
      second command reading DriveLetter from registry
      the third is packing an unpacked image file
   4) packing image & save to registry
         rdutil R: registry
   5) packing image & save to file
	 rdutil R: packed_file
   6) unpacking image
         rdutil unpack packed_file unpacked_file
   7) link NTFS junction to Ramdisk
         rdutil link temp \

7. Re-Format RamDisk
   You can re-format RamDisk except RAMDrive media type. eg:
   FixedMedia type
       FORMAT /FS:NTFS /FORCE /Q /V:RamDisk /A:512 R:
   RemovableMedia type
       ECHO Y | FORMAT /FS:NTFS /FORCE /Q /V:RamDisk /A:512 R:
   you can place your format command to startup script.
   I don't recommend re-format to FAT, the pre-formated RamDisk is
   more efficient than other format utililty.

8. pagefile support
   you can set pagefile to FixMedia type disk w/ pre-formated system.
   if you need other MediaType or re-format, use the addswap.exe utility:
       addswap r:\pagefile.sys 16 32
   create pagefile r:\pagefile.sys with min=16M max=32M.

9. TEMP directory
   you should set TEMP/TMP directory to TEMP sub-directory,
   don't use the root directory.

10. NTFS junction point to RAMDrive
   You can't create NTFS junction point to RAMDrive media type,
   Fixed & Removable Media type should work

11. Connectix VirtualPC compatibility
   someone report problem with VirtualPC+physical volume/disk.
   please set MediaType to RAMDrive/Removable.

12. Mountpoint without DriveLetter
   Clear DriveLetter registry value will not create Drive Letter for Ramdisk.
   Attn. Don't delete the DriveLetter registry, which fall to default R:.
   You can setup mountpoint/junction linking to this unnamed Ramdisk.
   eg:
	   rdutil link C:\ramdisk
	   	link C:\ramdisk to root of Ramdisk
	   rdutil link C:\TEMP TEMP
	   	link C:\TEMP to \TEMP at Ramdisk
	   rmdir C:\ramdisk
	   	rmdir can remove the link without clear target content
   NoDriveLetter configuration isn't recommended, because most AntiVirus
   software cannot realtime scan Volume w/o Drive Letter.


ChangeLog:
12.09.2003 fix SMP/HT compatibility
11.26.2003 fix re-format problem & some typo
11.25.2003 merge rdpack and rdj to rdutil
11.24.2003 add DiskSizeK registry, more compatible w/ antivirus software