BleepingComputer.com: Why am I losing free space from hard drive?

I hope I can present this all to you in an understandable manner, please ask me to explain it better if what I type doesn't make much sense. I'm mostly like a novice with some intermediate knowledge of computers, I think...

So I've been losing space on my hard drive for about two weeks now. Initially, I remember thinking "Weird, I was almost sure I had like 2gigs free, why only 500MB now? Maybe I downloaded something and forgot". I erased some things i didn't need and made a note about how much space I had. Checked a week after that, and I had mysteriously lost about 1.2 GB. After checking my C drive every so often, I can almost see that shrinking space, except recently that I started to write it down, there's not too much of a pattern:

yesterday:
09:00 802 MB (got offline)
13:34 879 (got online)
13:51 910
14:20 890 (after AVG finished, still online)
14:27 887 (just went offline)
14:40 888
14:48 887 (got online a few minutes ago)
15:24 881 (still online)
16:14 868 (online)
16:31 861 (got offline)
21:29 852 (just turned on internet a minute ago; was watching a DVD before that)
21:47 836 (internet turned off)
22:47 840 (still off)
23:15 840 (before sleep mode)

today, so far:
10:15 833 (online for a few minutes)
10:51 799 (still online)
11:46 790 (about to get offline)
12:37 789 offline
13:48 795 got online a minute ago
14:36 796 online
15:11 743 online
15:16 742 online (now)

Anyway, before really paying attention to my disappearing space, 2-3 days ago I uninstalled and re-downloaded and installed AVG Anti-Virus Free 8.0.238, Ad-Aware anniversary edition, and Spybot (and updated them too before running scans). Nothing major came up (and I've noticed in fact that Spybot reports finding absolutely nothing for at least a month now...it always used to find at least a couple of tracking cookies or something...). I never reinstalled Malawarebytes but just updated it and ran it, without finding anything. I was thinking it was a virus or whatnot, merely because I think I seem more space disappear when I'm online, which is why I noted it in my notes *points up*.

Oops, forgot to mention I have a Dell laptop (XPS M1210), Windows Vista Home Premium. I'm mostly sure my System Restore is turned off. I tried looking up similar problems on yahoo, and saw some people mentioned that the Shadowcopy things might be the cause. But when I ran the command prompt as administrator, and typed in that line of code to see how much space was being allocated(sp?) to it, I got a message that said something like... can't satisy the query. Anyway, I looked that up also and read that I think that means I don't have the shadowcopy thing on, so I suppose that's not it. But I may easily be missing something here.

I hope I've given you all the information you need, please tell me if there's something else (you'll probably have to tell me how to get it too, heh). Thank you for your help in trying to fix this before I have to erase something important as my hard drive disappears.

See
How to Free up Hard Disk Space on Windows Vista

Managing Windows Vista Volume Shadow Copies

15:28 742 got offline
15:43 793
17:01 786 just got online
17:13 786 just started Disk Cleanup (still online)
17:17809 finished Disk cleanup (I think 136MB were supposed to be removed), about to start Disk Defragmenter
17:20 808 assuming that's done, the cancel button changed to "Drefagmnet now" again like when I first clicked it
[skipped uninstalling programs since I've done it before and don't know what else to get rid of]

after typing in that vssadmin list shadowstorage command (again), it returns this:

vssadmin 1.1 - Volume Shadow Copy Service administrative command-line tool
<C> Copyright 2001-2005 Microsoft Corp.

No items found that satisfy that query.

--
I was afraid to do those downloads because I don't know if I need the considering the message I got about it not being able to even find it. Didn't do your second link since the same thing applies.

12:27 808 MB (still online)
12:39 808

Now what else can I do?

I'd suggest you check for malware on your computer. Read Preparation Guide For Use Before Using Hijackthis and other Malware Removal Tools, Instructions for receiving help in cleaning your computer Then post your log in this forum HijackThis Logs and Virus/Trojan/Spyware/Malware Removal

I think you somehow fixed it...

17:34 807 MB Got offline
17:50 807 about to put laptop in sleep mode
18:16 800 taken out of sleep mode, about to get online
19:17 799 got online
19:34 800 online
20:12 802 online
21:48 805 online
22:20 802 online, after doing hijack thing

It doesn't seem to be losing as much stuff, though sadly, none of the missing space came back :[ Thanks for the links though, I tried it out and posted my log file according to the instructions, hope that helps more, heh. Thanks again!

You're welcome - Since you have posted a HijackThis log, it is very important that you do not make any changes to your system. Why? Because by making changes to your system you change the picture of what's on your computer. So be patient and I'm sure they will get to your log.

cideon,

Now that you have an open HJT log posted in the HijackThis Logs and Malware Removal forum, you shouldn't make any changes to your system.
Doing so, could change the results of the posted log, making it difficult to properly clean your system.

At this point, the HJT Team should be the only members that you take advice from, until they have verified your log as clean.

I'm closing this topic until you are cleared by the HJT Team.
If, after your log has been cleaned, you still need help, please PM a Moderator and we will re-open this topic.

If you have any questions, don't hesitate to send me a PM.