Basically a delayed write failure is the fault of windows itself. For whatever reason, be it too busy at the time or whatever, Windows doesn't always write to a drive right away. This is also another reason crashes and power outages aren't good for computers.
Most commonly this is seen with USB storage devices when you just yank the drive out without doing the "Safely Remove Hardware" thing, thus why I asked if it was external. This is seen most often with programs like Microsoft Word, and other MS Office software due to the way it saves files.
It sounds like this happened a lot, and constantly. For some reason Windows was halting on writing the files in question. I can't say for certain why Windows was halting, and likewise I cannot rule out faulty hardware either. It could very well be the drive is bad, or it could just be a glitch in windows that just went away now.
Without a physical examination of the machine, I can't really say much more than that.