Files and folders mixed in Details view, XP Pro - can't change

Files and folders are mixing together but only on one drive or possibly in one folder. This drive in all places except two has a folder containing only folders or a folder containing only files. The exceptions are a folder called PVRRECORD and the root of the drive, which contains:

Then I move into PVRRECORD and things start messing up. Clicking on Name to arrange by name gives me mixed files and folders, usually (but not always?) with files of matching name to a folder coming after the folder. A file that you would expect to be mixed in amongst the folders may be at the end of the folders like a well-behaved file should be. Later it will end up mixed in with the folders like all the other files.

I found that clicking on alternate headings can cause the files and folders to separate and then clicking on Name again will give me the correct sorting order. However, I have to try Size, then Type, then Date Modified. Sometimes I only need to click on one other heading or maybe two but equally often I have to run through the whole lot before things go back to normal. Things don't necessarily arrange in a logical order, as you go through this process, until the last sort.

I'm using Details view but the problem still occurs in List view.

I can find plenty of hits in Google for people wanting to get this to happen and using "Arrange by groups" but I'm not using that, nor have I. I've tried going into a folder on my C:\ drive that's behaving normally and applying these settings to all folders without success.

Can anyone shed light on this annoying problem? It's one of those things that just seems to turn up out of the blue from time to time and if I recall correctly, a restart doesn't necessarily put it right. I don't want to try a restart at the moment because I'm partway through converting a large bunch of files.

The original file, in each conversion, is in a folder containing only files. The converted file is to be placed in PVRRECORD (with the same name but different extension) and then I move the converted file into the folder with the original and check the conversion was a success before deleting the original file.

Because of this silly behaviour, it's no longer possible to just take a quick look for files at the end of the folder list to find files ready for checking. If I weren't regularly moving back and forth around that window, into folders and out again, I know the files would just land at the bottom but as soon as I go into a folder and out again, newly created or newly creating files end up mixed up and difficult to spot.

I tried opening another instance of the Explorer window and it's even more badly behaved. There's no hope of sorting correctly. At the moment, in despair, I'm using two Explorer windows, with one arranged by groups and then size; it's the easiest-to-read view I can get but not what I want.

Please remember this is XP Pro, not Windows 7.

Thanks, people.