Backup: How Do I Scan Beforehand For Corrupted Or Deleted Files?

what I do regularly is simple backups of these files to external hard drive and DVD+RW's every x months. My point is that I don't keep different series of backups; I just keep overwriting my external drive and DVD's with the current backup, just to have the security of having a double of my data in a different geographic location in case of fire, flood, theft, etc. (knock on wood)

It occurs to me, however, that this system may not be entirely secure. What happens if, between the last backup and the current one, files on my system are modified in a way I didn't want? Or if someone else uses my computer and deletes files? Or if a file were accidentaly deleted, or even corrupted? In any of these cases, when I'd go do a backup, I'd be backing up a snapshot of My Documents that I don't quite want, because, unbeknownst to me, some of the files are corrupted or deleted, and it's not like I can go back in time and pull out a previous backup from (say) 2002 to recover a lost or damaged file. (The reason I won't keep previous backups is because I don't want to end up with an ever-expanding collection of dozens, and then hundreds of disks to keep in storage somewhere ... and even if I did, how would I know that the oldest DVD's in that pile weren't corroding and becoming unreadable over time...)

So what I want is this: a backup program, or separate application I'd run before the backup, which, when I come to do a backup, remembers the files from the last backup, and somehow compares the last backup to my current system (i.e. compares the previously backed-up files to what I'm about to backup), and tells me, before I proceed to overwrite the last backup with the current one, what has changed, in terms of which files are new since last time (obviously there will be new ones ... pictures, mp3's, docs), which ones are no longer there or corrupted (at which point I can make sure that the absent ones have intentionally been deleted since the last backup, and, if not, I can pull them back out of the previous backup and put them back on my system), before proceeding with the overwriting backup.

I looked at the different typical options, like incremental and differential backup, but they all involve constantly adding the new or modified files to an older initial backup, which always increases the number of discs you end up with. Also, those options will always keep the initial full backup on an old disc that's busy rotting away in the humidity. The way I'm talking about makes you always refresh your backup medium, and if your discs are no longer good, then you just replace them. In short, you would always have a fresh, full backup, and are sure that you're not copying corrupted files or that you're missing any, never to retrieve them again, because it tells you what the problems are before you proceed.

You see, normally, an incremental backup would be what I need, because it keeps an original version of the file, and then it keeps all incremental changes to that file over time, such as modifications. The problem with the incremental backup, however, is the principle that you're always needing more and more space to keep updating the original backup. If I'm backup up to DVD's, I don't want to have a new disc every time I incrementally backup my files. Also, how do you know that the original (1st) base backup, made years ago, doesn't now contain files that have become corrupted? Or the same for some of the earlier increments? Furthermore, there's the problem where, if you need to retrieve a file, you'd have to go back to the beginning, retrieve the original version, and then retrieve all the modifications across all the increments to get back to the version you want to get.

The way I'm talking about would be a rewrite your backup onto the medium (external drive, DVD's, solid state, whatever) every time you backup. That way, you always have a "fresh" set, and are not relying on an original base backup from 14 years ago + monthly increments, and don't have to worry about the original base backup itself having become corrupt after all these years.

Also, an incremental backup won't tell you what's missing or what's corrupt. Let's say you have your My Pictures. One of the folders is pictures from a Florida trip 5 years ago, and in it is a picture of when you had just caught a shark while fishing. That's a pretty important picture, and you want to keep it for all time. Well, meanwhile, you go on 20 more trips since that time, with 20 more folders full of pictures. 5 years later, you don't notice it, because you don't review old pictures very often, but that shark picture has become corrupt and irretrievable in your computer. Or, while viewing the pics from that trip one day, you accidentally delete it and don't notice. Or your friend or family member (for instance, a child) goes through your photos and starts deleting pictures. Or what if they open the picture in MS Paint and vandalise it by drawing a male member on your forehead. Now you come to do your backup of your whole My Pictures. If you simply overwrite the last backup with the current one, you're replacing a good copy of the shark picture with (potentially) a bad one ... or if it's been deleted, you're replacing the folder that had that picture with a folder that's missing it, and you'll never retrieve it again. If, on the other hand, you do incremental backups, then your picture is probably in the original base backup from 5 years ago, or else it's in one of the increments from 5 years ago, but who knows what the state is of the original base backup? Those original discs might be unreadable by now, and then there's the whole hassle of going up through the chain to get the pic. Not to mention that under this scenario, you have to notice yourself that a file is missing, and then take steps to retrieve it, as opposed to an application simply scanning and telling you so whenever you want.

Instead, there MUST be a way to do the full backup each time you back up (so you only have 1 set of discs to go into to find your files, and so that it's always relatively new, and not a rotten, corroded set of DVD's from 14 years ago), and that, before it actually does the backup, it tells you first what's missing, modified, added, corrupt between what you had the last time in your backup, and what you're about to overwrite it with now in your current backup.

I understand that the difficulty in indentifying corrupt files of any kind is that there are many different file types, and no program is so complete as to do that scan. But I guess I'm essentially worried about pictures, since mp3's and documents are less of a problem for me.

So really all I need is any application (not necessarily the backup program) to scan particular folders on my drive (only those I want to back up ... essentially My Documents, and not the whole drive) to check only 3 things:

1) which files have been modified (regular Windows xp search can do this if you advanced search for "files modified between ____ and _____", the 2 given dates being, say, the date of my last backup and the date of the current one);
2) which files are missing since the last backup (all this would involve is checking the files against a list ... seems simple ... and manually looking in Recycle Bin is obviously not enough because you may have emptied the Recycle Bin since last time); and
3) which files are corrupted

With the knowledge of these 3 things, I can take action to replace lost or corrupted files by taking them back out of my last backup. Then, I can safely proceed with the current backup.

I'm running XP MCE 2005.