How to change the default system of dual-boot using Wubi?

I have both Windows XP and Ubuntu installed.
I want to set Ubuntu as my default system when boot the machine.
I don't want to press Down+Enter every time.

I am using Wubi.

Original boot.ini:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect
C:\wubildr.mbr = "Ubuntu"

Modified boot.ini:

[boot loader]
timeout=30
default=C:\wubildr.mbr
[operating systems]
C:\wubildr.mbr = "Ubuntu"
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect

But nothing changed.

Click setting and select wubi as default operating system from drop-down menu. Click OK.

Assuming that you are using Wubi (saw boot.ini).

Use EasyBCD. It's a free program to modify the Windows Bootloader.

After you installed it, open it and go to the Edit boot menu Section.

Then tick the box beside the Ubuntu Entry under "Default".