I didn’t have any trouble installing Centos 7 to an unused 100G on my T-61 ThinkPad. However, Windows wasn’t listed in the boot menu (only Linux and Linux-recover).
This solution is from johnsfine, I’m summarizing for my own reference.
And fwiw, Centos 7 feels sluggish compared to Linux Mint 17.
After installing Centos 7, sda1 remained the bootable Windows partition and was untouched. However, it seems Centos7 does not support the ntfs file system out of the box. This means at the end of the install, when grub2 probed the drive to build the boot menu, the Windows partition was undetected and therefore wasn’t added to the boot menu. This procedure solves that.
After adding Windows to the boot menu, the default boot is still Centos 7. I would like to change the default boot to Windows, but it seems complicated. Maybe someday…
Enable the EPEL repository (directory and filename current as of this writing)
wget http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-2.noarch.rpm yum install ./epel-release-7-2.noarch.rpm
sudo yum install ntfs-3g
grub2-mkconfig -o /boot/grub2/grub.cfg