Both partitions, with the windows and the other one were formatted and merged into one not unpartitioned space. Is there a way to recover the data with some bootable program or should I install the operating system first and then some software for recovering? Is installing the OS going to overwrite data?
How can I access and get those 16.91GB of data?
You should definatey NOT install anything new on the disk as it will overwrite data. Try getting a linux usb recovery distro with Photorec (and another disk drive to write data it can recover too).
You can try with Hiren’s BootCD. They have whole section with Recovery tools. And don't install OS on that drive, don't write anything on disk.
