Sounds like F3 or F4 could have done that.
Data loss can occur any time you spill fluids in your keyboard.
If you're investing a lot of time into a document, such as an essay for school or a videogame playthrough for fun, you should back up the files.
If you had backups if your .dsv battery save document, you could restore it. Maybe you already have a backup solution running on your system from which you can restore an older .dsv before you accidentally.

And that's not emulation, anyway. It's viewing the hardware on your PC. It's basically the literal exact opposite of what was requested here: viewing the emulator on the hardware.

ask your security software, check eventviewer for information about why desmume is crashing when you close it instead of saving its settings and closing properly, or ask yourself why you had to put it in program files instead of on your desktop.

then you ask your administrator to change the time on the PC, or edit the source code and rebuild it.

change your config > display method. Some graphics drivers are incapable of doing old directdraw clear commands. It seems yours is one.

They keep porting updated things because it's easier than merging upstream. We still need whatever "improvements" they put in desmume (otherwise we will then have libretro/desmume2014, libretro/desmume2015, libretro/desmume, libretro/desmume-reloaded, libretro/desmume-upstream). I'm not going to sanction creating a new fork. We need to do this right, and merge the wifi along with whatever "improvements" libretro does so that there is no doubt what to use.

note that libretro's "improvements" often consist of things like
1. deleting features they dont care about
2. cosmetic changes which contribute nothing but merging grief.
3. build fixes for other platforms -- very useful, but mixed in with the other garbage

it's stupid, but that's what we have to work with. we need to isolate the all the good values so I can go tell libretro we have an official libretro upstream that they have no reason not to use, and now they need to use it.

retroarch forked desmume for whatever reasons. we don't need to paste what libretro did into our repositories ourselves; they could do that if they thought it was wise and the time was right. I assume they've made more various modifications dispersed throughout the desmume code. have you incorporated libretro's own work, including those modifications? I cannot tell since your first commit already had that work in it. Or is your libretro implementation your own? It would seem so, since you credited yourself for it. We don't need someone else's libretro implementation unless someone from libretro says it's ace.

That URL is broken.

And we would have noticed if changing 3d settings broke games for the past 6 months. your gpu must be dead. blow the dust out of the fans or something. I guarantee you 100% if you put in another GPU the problem will be gone.

For the record, here's wackobo's thread full of raving:
http://forums.desmume.org/viewtopic.php?id=11118

windows is trying to make it act like a mouse. that's how it makes it act like a mouse. first tap moves the cursor, second tap clicks. look for some option in your tablet driver settings

That's weird. Why would it store whether the existing pixel is front or back facing? Unless it's for shadows, I can't see any reasonable use for that. I don't see how it would be useful for shadows, but it seems possible--an the behaviour here would be a side effect of some hack meant specifically for the shadows

There's only 7 buttons. have you tried clicking them all?