When I tried to download something off the internet, the thing stopped because it said I had "no more free space," though the disk usage analyzer says I haven't used even half of my 8 gigs left, and the file is only 450 mbs. Do folders have their own maximum file space or something?

Directories (folders) don't, but partitions do. Have you tried running df -h and checking its output for 100% full partitions? It may be that you have space on your drive, but not in the drive's partition that you're writing to.

Maybe going to /tmp - let's see the output of "df -hT"

I'm sorry if I'm sounding really dull right now, but I went to /tmp in the directory and ran both df-hT and df-h, and it said that it wasn't a command.

To clarify a bit, I have a wubi installation right now. If you don't know what wubi is, it's a newbie installer for Ubuntu that installs Ubuntu directly into Windows. I think it has it's own virtual partition or something. I ran the disk-usage analyzer, and it said that I was using about 3 of my 8 gigs. In all, my hard drive can store up to 37 gigs, so I'm pretty sure that disk-usage analyzer is taking a look at my partition or whatever it is that wubi is making.

Whoa, just looked at my file browser and it's telling me that there's 423.8 mbs of free space only. What accounts for this disparity?

The command is "df"; "-hT" is a parameter - stick a space (blank) between them.

Wubi looks like a loop-mounted Windoze file - not a virtual environment despite the name of the file. I don't use Disk analyzer, but in that environment it should be giving you the correct numbers - file browser will depend on what directory you are in.
Lets see that "df" output.

Just to make sure you type it in correctly this time, here are the exact commands we would like to see:

Just type of those commands as seen, and show us the output.

Got it, here's what it returned, don't really get what it means.

ext3 7.8G 3.0G 4.5G 41% /
varrun tmpfs 252M 100K 252M 1% /var/run
varlock tmpfs 252M 0 252M 0% /var/lock
procbususb usbfs 252M 100K 252M 1% /proc/bus/usb
udev tmpfs 252M 100K 252M 1% /dev
devshm tmpfs 252M 0 252M 0% /dev/shm
lrm tmpfs 252M 33M 219M 14% /lib/modules/2.6.20-16-generic/volatile
/media/host/wubi/disks/home.virtual.disk
ext3 939M 938M 0 100% /home

It's saying that your home partition has used up all of its space (it's at 100%). You need to either free up some space (move files to another partition or a CD/DVD/USB stick) or re-partition. Moving files is quicker and easier, re-partitioning is a longer term solution.

If you decide to re-partition, you should back up your data first - murphy's law seems to be very fond of personal data...

Run thisThat will list the likely bad boys.

Tried that thing that told me what my file space eaters are, found out I didn't need them, so they're saying bye bye pretty soon.

But what's the 7.8 gigs thing at the top of my output then? I can assure you that my total hard disk is about 37 gigs, and Windows only uses about 16 of those.

The top partition is for the "root" filesystem ("/"), right now your personal files have their partition, so all thats housed in the root filesystem is the OS related files, such as programs, system wide configurations, program related resources, etc.

Tho, its usually customary that your personal files will be larger then the OS, so you should really consider expanding that measly less then 1G of your personal space to something more realistic.

Ah, so personal files don't get there space counted with OS files.

See, Wubi did all of this partitioning stuff for me, so I had no idea that I would only get 1 gig for myself! Is there anyway to share those OS files with my personal files, because one of the reasons I used Wubi was for its lack of me partitioning (I'm pretty paranoid about file loss, even though I backed stuff up).

Do you mean have both sets of files on the same partition? Yes, thats very easy, there really is no good reason to have them on separate partitions, other then trying to prevent total dataloss should a filesystem get corrupted.

First step: create a new directory in the "/" directory, call it "new_home" or whatever. This will require you to be root. Next, copy everything from /home into /new_home. Once you verified that all the files you want are there (including your user directory, dont want to miss that), you must remove the /home filesystem. The command "umount /home" should do the trick. Now, /home should be a empty directory, make sure that it is before continuing. Next, replace /home with /new_home. Dont turn off your computer, but now login as your user. If you where successful, the login should work and everything should look normal. Once you verified that it is, there is only one last step in the process. The /home partition you have set aside will still be mounted on boot-up, nothing irreversable will happen, but its fairly annoying having to un-mount it every boot-up. Edit /etc/fstab and find the line that has the information about your /home partition and filesystem. Simply comment it out by placing a "#" at the start of the line, that should prevent the filesystem from mounting itself at bootup.

That sounds great, just two questions:
1) Will this get rid of the old home partition and fuse it back with my linux partition?
2) How does one replace /home with /new_home? Just delete one and rename the other?

It's saying my device is busy when I try to umount /home! What do I do?

1) Nope, merging partitions can be a royal pain, its better to simply do a complete format and reinstall in this case (it will also delete all your files), but the partition itself can be reformatted with a new filesystem and you can use that in case of emergencies or when you need extra storage space.

2) The safest way is to copy the contents back into /home, then delete /new_home once you verify the system is working after a reboot.

Ah, i think i forgot to mention, if any files are open to that partition, then you cant umount it. You must close all files, this will probably mean having to stop X, logout of your user, and login as root, this should leave you with a nice text based interface.

Another possible solution, is to try the command "unmount -l /home". This command might not work, so you must be sure to verify that it completed by looking at /home and make sure no files or directories exit. I would say try this command first, as it might be easier.