chuotnhat,
I'm sorry to hear that you're having issues with your Windows 7 machine and your sound card. I know how frustrating it can be when your system isn't working properly. You might want to consult the Windows 7 forum at microsoft.com/springboard, there may some information about compatibility with your system, please keep in mind, if your system was stable before, and you have the Vista Drivers they will work with Windows 7, so you may want to revert to them.
Thanks,
v-glferg@microsoft.com