My sister's computer has stopped working. I am not entirely sure what the problem is, but I think it is a Windows/software issue. She really just wants to retrieve the pictures off it. I am wondering if I could install a Linux OS (CentOS is the only one with which I am little familiar) on the free space and access her Windows file system. I know there are several 'what ifs', but is this a possibility?
First you'll have to make sure which hard disk and partition Windows is occupying, let's suppose it's on /dev/sda1.
Open a terminal, run
# mount -t ntfs /dev/sda1 /some/random/empty/directory/
Your Windows files should be accessible from the directory then.