The sudden transformation of your dissertation into symbols; the failure of an application like QuickBooks to recognise a legitimate file it previously accepted; a wedding video which only plays for 4 seconds and then stops playing: all are examples of corrupted data. The data is present but corrupted; therefore, fixing this type of corruption will depend on where the corruption occurred: at the level of the file, the file system or the hard drive upon which both reside.
Corruption that occurs at the drive level can include failing sectors in a drive causing files that were written to those sectors to contain “holes” within them. This represents the symptoms of a failing physical hard drive where the primary focus should be to create an image of the failing hard drive prior to “just a few odd files” becoming “the entire drive will no longer mount”. Corruption occurring at the file system level can manifest when there exists confusion with how names link to their respective contents. Files may disappear, folder entries become gibberish, drives ask to be formatted, and although the contents themselves remain intact they require reconstruction. At the file level, the document was damaged, either by being interrupted during a save operation or by a program crashing while writing changes to it; recovery involves repairing the structure of the document. For example, headers are rebuilt, streams are salvaged, text and graphics are extracted from Office documents and video is remuxed as its index never made it into the video. The diagnostic pins down the layer first, because treating the wrong layer wastes the patient.
The file-level cases: straight talk. Repair reconstructs structure, not missing substance. A Word document with good text but bad packaging will get fixed in full; a video without an index will get remuxed and play; a spreadsheet with bad formulas can still give you the data even if Excel says no to the file. Content that was never created (the crash occurred before it had been saved) is unfixable; a file whose middle third is all zeros will still have a hole. Our findings by file (repairable, extractable or lost) are provided free at diagnostic time, so you know what you're doing before you make your decision.
Typically not: a "symbol salad" is usually a damaged wrapper around content that has survived, and text can be extracted even from documents which Microsoft Word will refuse to open. Get a quote first, over the telephone or via the quote request form, then send the corrupted file, along with any temporary copies and backups, for review; Office frequently spreads pieces of the damaged file into other files, and the recovery can weave those in.
Yes, classically that is a missing or truncated index, which often occurs when recording has been interrupted, and re-muxing creates another wrapper in which all footage is fully present. If you can get your hands on the camera or card it came from, send it to us too, as soon as you have a quote by phone or with our form, because the original source sometimes yields a cleaner copy.
Mass corruption is a symptom, not a coincidence. A broken disk, a tangled file system or malware is likely to be the root of it. Stop using that machine, and especially stop running any kind of file repair utility on it. Get a quote first, either by calling us or filling out our contact form. Then bring your drive in to us (no appointment needed) during business hours; we are open from 9am to 5:30pm, Monday to Friday. Fixing files one by one while the cause is still running is like bailing a boat with the plug out.