If you install a HD over 8 GB in an older PC it will format it as 8 GB. Learn how to correct this problem..
In older PCs BIOS doesn't support hard drives over 8 GB even though the hard drive is correctly recognized on setup. So, it will be correctly recognized on setup but when you format it, it will only format as 8 GB. This problem is caused by a BIOS limitation, similar to the famous 504 MB limit that existed many years ago. Read more at HardwareSecrets