Can't find Finder and Dock and Desktop has disappeared

Question

I was backing up my MBA (OS 10.6.0) today using Superduper and something strange happened.
My hard drive became corrupted and filled with files (105 GB used and 0 GB available). The HDD capacity is 120GB. About 15GB is bootcamp. The backup failed.
I deleted a few files and freed up 200MB when I realized the hard drive had become full (I had 20GB free space on the Macintosh HD before this).
When I checked Disk Utility it told me my hard drive was corrupted and I should repair it using the operating system disc (Snow Leopard) to start up the computer and then go to Disk utility and perform Repairs.
I did all that and Disk Utility told me the hard drive was OK after the repair.
However, when I restart the computer, I get a blue screen. I cannot see the Dock. And Finder cannot be found. When I do Force Quit, there is no Finder in the list.
For some reason even though I do not have a Dock, I was able to get a menu at the top. I don't know what I did to get it. Suddenly I got a message saying I couldn't open iTunes even though I didn't try to open it (the Dock has disappeared). But at least I got some menu at the top.
With the menu I was able to open some items on Recent Items including Firefox.
I went to my email and tried to send some files to the same email address. I was able to browse Finder by doing this and my Desktop seems to be OK. I can open various files by using the browse function in upload files in my email and they all seem OK.
So I know that my Desktop files are intact. I haven't checked them all (I have like 50 files on my desktop) but on a quick look, all the Desktop items appear to be there.
How can I get the Desktop and the Dock back?
How can I get Finder to show up?
I just have a blue screen at the moment.
When I get the Desktop back I want to erase some files and create space.
Somehow the hard drive got filled up when I tried to do a backup using Superduper.

Answer 1

All resolved.
I attached an external drive to the MBA in an attempt to export Firefox Scrapbook files onto it.
Exporting failed (my fault – I didn't follow the steps correctly) and I ended up having to restart the computer.
Surprisingly the screen opened in bootcamp.
Because there was an external hard drive connected to the computer, I presume this is what prompted the computer to open in bootcamp. Normally I would have to hold down the Option key to open bootcamp but my computer's hard drive had been corrupted so ....
From bootcamp (Windows XP) I restarted the computer, this time holding down the Option key.
I selected the Mac volume as the startup disk.
When it booted, it sputtered a few times and it looked like it was going to open in the blue screen again (I could see the familiar strange things that occur when it opens in the blue screen). However, after a while, it opened with the Desktop screen.
All the icons I had on the Desktop appeared and I had the screen back to normal with Dock and everything there.
I deleted some items (I only had 200MB left) to create some room on the hard drive.
After browsing the web, I came across the reason for why my HD suddenly filled up during the failed back up before things went awry.
From Pink Mutant
http://pinkmutant.com/articles/TigerMisc.html
"Failed Backups and the Volumes Folder
Another potential stealer of hard drive space is a failed backup, where the drive the backup was supposed to go to was unavailable, so the backup software simply copied the files into the invisible /Volumes folder. Again, use the Go and Go to Folder menu bar item ....."
This is exactly what happened to me. I found the two volumes, "Untitled" and "Untitled 1" as Pink Mutant said I would in "Go" ("Go to Folder") and I deleted them (I should have backed up my computer before doing this though). Straightaway, 20GB of space came back on my HD.
My computer had copied the backup onto my HD instead of the external HD during the failed backup operation. That's why the internal HD filled up.
So it's a relief that I got the Desktop back again – purely by accident – and I also found what was filling up all the HD space.
So a tip: if someone finds their backup fails for whatever reason, don't try to back up again. Check HD space and if it has suddenly shrunken, go to "Go", and then "Go to Folder", type "/Volumes" and click "Go". That should bring up the offending volumes if any. Move them to Desktop. Check "Get Info" and have a look at the contents if you can (I couldn't). Do a backup of the computer. Then delete the problem volumes (if you find that these volumes are the cause of the problem). You can then delete the same volumes from the backup at this point.