I hope you have backups as we're forever telling people on here to save everything at least twice, especially when it comes to pics. Plenty for free storage places around.
These external drives fail more often if you're moving it around quite a bit. Regardless of age/usage they can fail at anytime. If you can't get it recognised in Windows try DOS, but even if you can get on it the only option may probably be to reformat it. Try CHKDSK D: /F or what ever drive letter it is.
