I don't know how to go around M$ way of writing directly to a diskette unless u use 3rd party tools like BackupExec IDR.
I got this script somewhere when I was researching for auto backups a long time ago.
Create a Windows 2000 ERD using Window Scripting Host.
1. Open the Backup GUI by navigate to the Accessories folder, then the System Tools folder and opening the Backup GUI.
2. Press the Emergency Repair Disk button.
3. Check the Also backup the registry.... box and press OK.
4. Press OK and close the backup when it is finished.
You can convert the above to a hot key, or icon press, if you create a shortcut the the following .vbs file:
set WshShell = CreateObject("WScript.Shell"

Wshshell.Popup"Please insert blank floppy disk in the drive A:"
Wshshell.Run "ntbackup.exe"
WScript.Sleep 500
Wshshell.Sendkeys "{ENTER}"
WScript.Sleep 500
Wshshell.AppActivate "Backup"
Wshshell.Sendkeys "{TAB}"
WScript.Sleep 200
Wshshell.Sendkeys "{TAB}"
WScript.Sleep 200
Wshshell.Sendkeys "{TAB}"
WScript.Sleep 200
Wshshell.Sendkeys "{ENTER}"
WScript.Sleep 500
Wshshell.AppActivate "Emergency Repair Diskette"
Wshshell.Sendkeys "{ }"
WScript.Sleep 500
Wshshell.Sendkeys "{ENTER}"
WScript.Sleep 20000
Wshshell.AppActivate "Emergency Repair Diskette"
Wshshell.Sendkeys "%{F4}"
WScript.Sleep 500
Wshshell.Sendkeys "{ENTER}"
WScript.Sleep 500
Wshshell.AppActivate "Backup"
WScript.Sleep 500
Wshshell.Sendkeys "%{F4}"
WScript.Quit()
NOTE: If you computer is slow, or a Service Pack changes any of the Wshshell.AppActivate text, running this script may have unpredictable results, including forcing a shutdown. So Therefore TEST TEST TEST TEST TEST...