Sony Xperia SP C5303 not booting into fastboot mode

Device: Sony Xperia SP C5303. I turned off the device, then hold volume up key, and plugged the USB cable. But I see no blue light. After a while it goes into charge mode. What could be the problem? Some additional information: I'm on Windows 7, 64 bit. I downloaded this driver http://developer.sonymobile.com/downloads/drivers/fastboot-driver/ and overwrote the one in c:\Users\MyUserName\AppData\Local\Android\android-sdk\extras\google\usb_driver\