If it doesn't show up in Disk Management, either in this PC or in another one, all you can do yourself is try if it turns up in Linux, either in the File Manager or in the default partition editor GPARTED present in most distros. A Linux disc or stick to boot from can be made for free (for example, Mint or Ubuntu) or download and burn the GPARTED disc.
If it doesn't show there either, it just broke. Can happen with 9 year old disk. Then find a data recovery company like driversavers.com (or many others) to get your important data off it. That's not free at all, but hey, think of the time you saved by not backing up for 9 years