I can't agree with that. If one installs GRUB on the boot partition rather than the MBR the system will not be able to boot CentOS unless you install some other bootloader or figure out how to convince Windows 7 to load it.
The real trick is making free space on the disk for CentOS. The RHEL/CentOS installer does not deal with NTFS due to TUV
's concern about legal issues.
One trick is to use a recent Ubuntu distribution install procedure that does know how to shrink the Windows partition. Kill the Ubuntu install after it finishes the partitioning and tell the CentOS installer to overwrite Linux partitions. Write the GRUB bootloader to the MBR and it will automatically add the Windows partition as "Other". You can edit that to use a more descriptive label.
One issue I have run into with recent Windows systems, that have the restore/rescue system on disk rather than providing DVD media, is that they use 3 of the 4 primary partitions! The only way to handle it seems to be to remove at least one of the partitions, after creating the restore media and before shrinking the Windows partition, in case you ever need to get back to the factory configuration. The primary Windows partition should still boot.