Here is the procedure:

In the morning

1. I installed ubuntu using a USB directly without config any thing to my win7 system.
2. After install complete, ubuntu installation software tell me to reboot.And everything is just find.
3. While rebooting, there is NO UBUNTU system for me to select,and my laptop go straight to log in using WIN7.
4. NO ubuntu shows on WIN7's configuration(Default System).
5. Log in ubuntu using usb(try ubuntu without installation), I can find ubuntu's filesystem was already there.
6. Formatting the disk on WIN7's disk management, rearranging them to other disk.Still having no trouble with WIN7.

In the afternoon

1. try a few times of installation and uninstallation of ubuntu.
2. still shows no sign of selecting ubuntu system.

In the evening

1. another trial while installing ubuntu with the third option of:
   1. installing ubuntu alongside with INW7,
   2. erase win7 and install ubuntu.
   3. somethingelse --- my check
2. failed with configuartion for what comes out with the 'something else' option,reboot.
3. And I have no system now with some cmd tips say:
   1. Reboot and Select proper Boot Device or Insert Boot Media in selected Boot device and press a key.
4. Files those on win7's orginal file system and Ubuntu filesystem can still be found when I 'try ubuntu without installation'. 5.But I just got no OS when I reboot my laptop normally.