Flashing grey screen and background pic when log in, can't access anything!

Question

Please bare with me, this is a long one since I'm including every little detail in hope that it helps my desperate situation. I have been receiving "startup disk is full" messages for about a month now on the MacBook Air OS X Version 10.8.5 I bought new last summer. I am currently traveling throughout Asia with limited internet access, but am working from the road, which makes having a working computer critical. I checked online and followed all the advice I understood on how to clear up space: moved all my documents and pictures to Box/Dropbox, deleted unused applications, and emptied my general trash and iPhoto trash. This only stopped the startup disk full messages for a week before they started coming up again and again. I checked my storage and it said the "Other" was taking up most of the space. I realize that this could mean any number of things.I downloaded omnidisksweeper, but didn't want to risk deleting anything when I didn't what they were for. If I remember correctly, of the things I recognized, it said that my Mail was taking up a lot of space, but that made sense since I have 3 large accounts I work from. I deleted the couple files that were in the "recovered" file. Last week one of my email accounts kept resenting me the same 30 messages for a couple days. I couldn't figure out why. A couple days ago, I went to turn on my laptop after shutting it down the night before. I was able to log into my user, but once I logged in, my background picture and this blank, grey screen started alternately flashing. My dock on the bottom does not show up. In the top right corner it shows my Dropbox box icon (which I can click on and it says it's up to date, but nothing happens when I try to open it) but none of the rest (battery, Internet icons, etc). When I click on the apple in the leftmost corner nothing happens. In the top left corner the Finder toolbar shows up, but the drop down menus only open sometimes. When I click on anything from the drop down menus nothing happens. Sometimes a window pops up that says that "the last time you opened Finder, it unexpectedly quit while reopen ing windows. Do you want to try to reopen again?" The the meantime that grey screen is still flashing in the background. I have chosen "don't reopen" and "reopen" before, but nothing happens. I tried pressing down control, command, delete as suggested but nothing happens. I end up having to hold down the power button, and choose the shut down when the usual shut down, restart, sleep message shows up. I am able to access the Guest User account without problems and created a new User. However, the disk is, of course, still full, so I'm right back where I started, except that I'm unable to access my main user account that actually has all my stuff on it. I searched online and haven't been able to find anything similar to my situation. Please give me any suggestions you might have, I'm in Indonesia at the moment and have nowhere I can take it for help, but still need to work! I'm not very tech savvy (obviously), so please try to be specific! I've run the disk utility "Verify Disk" thing but it says everything's ok. I downloaded omnidisksweeper again onto the new user I created with the limited space I have available, but don't really understand what anything on it means! It says that most of the space is taken up as follows: 9.5GB private, 4.5 GB applications, 3.7 GB system, 3.6 GB library.
Is there anything  specific I should be looking for? Is there anything I can do to get my original user account to work?

Answer 1

Welcome to the Apple Support Communities
If you don't remember the password, you have to reset it. As you have a new MacBook, you are using OS X Mountain Lion, so follow these steps > http://discussions.apple.com/docs/DOC-4101