I first installed Windows 7. /dev/sda1 was the system reserved partition for Win 7, and /dev/sda2 was the C partition. Then I installed Linux Mint. After that, when I started the computer, I could see the "Windows 7 (/dev/sda1)" was listed in the end of boot menu, but I could boot into Windows 7. The only thing I can think of is I might make a mistake in choosing the place the grub was to be installed: I chose /dev/sda1 rather than /dev/sda by default.
Can anyone provide any advice? Thanks so much!