I ran disk cleanup and got rid of some files I no longer needed while backing up some of my data just in case. During the process, I watched the amount of free space climb to larger than it should have (considering how much space I cleared). It stayed there for a while then plummeted by five or so gigabytes down to another level. It stayed there for a couple of minutes then lost 200 MB of space.
It stayed that way for a few days, then one day I started it up and another 100 MB of space was gone. I observed the hard drive space over the course of my time using the computer that day, and it kept fluctuating by 100 MB - sometimes gaining and sometimes losing. This was while I'd not saved, altered, added, or deleted anything of such a substantial size.
Now, it has settled into this bad and terrifying habit of eating 100 MB at a time - mostly randomly but often when the system is booted. Sometimes it returns the space for an hour or so then takes it back, but it usually just eats away at it. Over the course of the week, I've gone from 54.1 GB free space to 53.8 GB of free space and all I've saved is roughly 42 MB worth of music and image files. In fact, it jumped down to 53.9 GB and then, when I hadn't saved or altered anything it decided to jump down to 53.8 GB.
This is becoming faster and more worrisome as each day passes, and I have no clue what could be wrong with my computer. Obviously, I don't want to have to buy a new one or face losing everything that's on this one (I couldn't afford a new one, anyway), so any help would be greatly appreciated.
For reference, I'm using Windows Vista Home Premium on an HP Pavillion dv7z notebook computer (the AMD-processor version of the dv7). I'm no longer familiar with how to find the details of my hard drive aside from how much space it claims is being used, but I'd be glad to share if someone would tell me what I need to explain and how to find said information.
The only things that I can think of doing that may have caused problems are: I began playing the game ADOM for Windows (Beta version 4, I believe), originally from a local installation but then from a USB flash drive installation; I used a friend's flash drive to install software for my new mouse; my battery died completely (I just installed the replacement today); my computer suffered through two power outages and one low-voltage 'surge' (which the surge protector claims to have caught); I burned backup copies of two of my DVDs with almost-cracked hubs; I tested a layout online in IE and encountered an ad that froze the fickle browser; and I moved a few files around to clear off my desktop from clutter.
If anyone can help, please do. I'm afraid that my hard drive space is never going to stop vanishing at this rate.