Okay, I've asked some really dumb ones before, but this one will take the cake. And most reading it will be convinced I'm nuts (if they weren't before) but here goes...

My hard drive is only 250GB. As such, I have always kept a close eye on how full it's getting. And it was recently hovering between 100 and 110 GB free.

Now, out of the blue, and I SWEAR I didn't install any new programs, it's suddenly down to 80. WTF?

How can I figure out what's caused the drop? And suddenly a directory entitled Windows.old is showing up. It doesn't have 20 GB of data in it (only 1 file as far as i can see) but I thought that directory only showed up when you upgraded Windows versions. I did not do that.

7IXB8-P3X4Q-L6ZZJ

This vampire game is on Steam and if you're interested you will need to change the "X"'s to "E"'s and the "Z"'s to "T"'s.

Windows update sneak downloading w10 update files?

I imagine it is some manner of logging, which for some reason took off with reckless abandon. Try emptying various caches and temporary file repositories. Browsers let you empty their cache and Windows lets you clear up all of the stuff it accumulates. See if that returns your 80 Gig back to you.

This. At least that's the first theory that popped into my mind.

Oh, sorry. Guess I should've explained. This always has been a Windows 10 computer. It's an ASUS ROG laptop purchased in 2016 and it came with Windows 10

because of automatic updates and automatic restore points.

Windows 10 installing Ubuntu Linux?

I was thinking maybe an automatic update, as I know I've had one between the time when it was 100 GB free and now when it's 80GB free.

But a 20GB update? Wouldn't that have gotten some pretty serious attention and I would've heard about it?

I'll try this.

WinDirStat is a good free program for analyzing disk usage. You can sort by recently modified. Caveat: I haven't used it on Windows 10.

From wat u describe, it seems like ur comp auto-downloaded & installed the Windows Anniversary update. For more info, pls c the below link:

http://www.laptopmag.com/articles/anniversary-update-wasting-space

Hope this helps. :)

Oh, i took ur steam key as it looks kinda interesting 2 me. Hope u dun mind.

If you're using GOG Galaxy that be the culprit. There have been some people reporting that some log file is keeping data stored when it should be rotating it. I don't understand it but it's been discussed in the GOG Galaxy sticky along with some threads in General Discussinos.

I fail to see why this would be a dumb question... 0_o

As others have suggested, try some tool like WinDirStat or TreeSize Free to see if some folder is blowing up. Be sure to run them as admin. I like TreeSize, because it's really easy to see where application dump data that just keeps growing and growing...

You could also try system cleanup (in admin mode, which lets you delete the Window Update installers). It shows you how much space it could make free and where - if there's a lot at the Windows Update stuff, Anniversary Update may well be the culprit.

Not sure how to do it in Windows 10, but in my Windows 7 I'd do these steps (and I do these time to time):

Run the "Disk Cleanup" utility (does Windows 10 have it too?).

- Select the drive and Ok.

- After it has scanned the drive, click on "Clean up system files". At least in Windows 7 this restarts Disk Cleanup and rescans the drive.

- Go to the "More Options"-tab and click on the "Clean up" which is under "System restore and Shadow Copies".

- After that go back to the "Disk Cleanup"-tab, tick on all the boxes, and press OK.

After that I might also clear the temp directory:

- Type %temp% either to the Start search box, or to Windows Explorer address bar, and press Enter. This should move you directly to your temp file directory.

- Select all the directories and files you see there (Ctrl-A), and just delete them.

- If it refuses to delete some temp files/directories because they are in use, let it skip them. Obviously you shouldn't try to delete any temp files which are currently active, but everything else can go as far as I can tell.

I usually reboot Windows after this, maybe it it is not needed but whatever.

Depending how long it has been since I've done that, this usually frees up quite many gigabytes of hard drive space, at least in Windows 7.