The only sticker is for XP Pro. I gather the IT department at the company installed a W7 Ultimate on it "as a favour". However it wasn't a valid copy so was always giving her problems.

When I replaced it with XP I used the sticker key.

It's a commercial DVD that plays fine on my own XP PC.

You should also do her a favour, just do a proper job of it.

Okay, last try, install k-lite & maybe select a region in the DVD player device properties panel.

You haven't said what kind of HP PC it is.

"inherited the PC when she left work" may make it the HP equivalent of a Compaq Deskpro PC or modern equivalent. Native HP home PC would be a Pavilion (or worse, a Compaq Presario). The home PCs can be quite different beasts from similar-spec business PCs (or at least used to be, in the days of XP...).

It is vaguely plausible that there are differences in the graphics (and other) drivers between the HP/CPQ version and the vendor (ATI or whoever) version, especially where multimedia is concerned. Whose drivers are you using?

There was often an HP/CPQ-supplied DVD player downloadable from the support site if one was supplied orignally.

If it is an HP business PC it is possible that it has cheap+cheerful integrated graphics AND an add-on graphics card. This too can confuse the picture.

Have a look at these, and report back.

Mind you, none of these would directly relate to WMP saying "no DVD decoder found". But maybe that's only what it said, not what it meant.

Best of luck.

It's an 'HP Compaq Dx 2200 Microtower'.

Many thanks. K-lite Standard in conjunction with its Media Player Classic now plays DVDs.

Windows Media #Player crashes, VLC hangs.

As it happens I'd already tried K-Lite but had only downloaded the Basic version which, had I read it properly, I'd have seen doesn't include an MPEG-2decoder for DVD playback - Doh!

So it's now set to default to Media Player Classic for DVDs, WMP for CDs. All works fine.

Just take WMP out of the equation for a minute, if you load VLC and try and play it in that dies ut play at all?

I said at the beginning VLC doesn't work, as I recall it just hangs.

But as I've already posted I now have a solution via K-Lite which works.

You need to alter "Subject" and add "fixed".

Makes it easier to know in which post you found a solution.