Can't download applications (poss due to hard drive space issue)?

Question

Hi there,
I'm having major hard drive issues with my MacBook Pro OS X 10.4.11 2.4GHz Intel Core 2 Duo 4GB 667 MHz DDR2 SDRAM laptop.
I use it for video editing and also keep music on it. However for the video editing I use an external hard drive, though I've found some Final Cut Pro files on my internal hard drive before and deleted them whenever I've found them. Sometimes it's an Imovie project, sometimes a straightforward final cut project, sometimes a playout of a final cut project.
My problem is that I now have almost no hard drive space, to the point where I wasn't able to save a Word file last week due to insufficient disk space! I emptied the trash and managed to get it to save in the end.
I immediately went on to the discussions pages and it was suggested to try WhatSize, OmniDiskSweeper and Disk Inventory to identify the files that were taking up all the room. Unfortunately NONE of these applications will download onto my laptop. They're not the only ones, I tried downloading a couple of other applications for music and the like and NOTHING will download!
I went through everything that I felt I knew for certain that I could delete without being detrimental and freed up a small bit of room and tried again but still NOTHING. I then used Onyx on the suggestion of another post and freed up a few gigs (I went from 1.7gb available to 7gb available) and assumed that this would do the trick, however, it hasn't!
What happens when I try to download these (or any) applications is that when i click the "Download Now" area on the webpage it begins to move onto what should be a download progress page or a "download complete" page but instead just spends an eternity "loading", with the little loading wheel on the left of the tab just spinning around and around. I tried leaving it literally all night last night but to no avail, opened it back up again and still the circle was spinning around and around "loading". This has been the case for the several dozen attempts I've made, no matter what the website.
It seems like something of a Catch 22 if the situation is that I can't download these applications that will help me to free up Hard Drive space, because I don't have any Hard Drive space! Though I'd have thought that the 7gb I now have would be ample. Did my laptop turn to self preservation mode perhaps when the hard drive was down to the bare minimum and I wasn't even able to save word documents?
If anybody can help it'd be HUGELY appreciated...
All the best,
Rory

Answer 1

If you open a Finder window you can also sort by size by clicking the size column header. In view options you can also set it to calculate all sizes so it will also show folder sizes. Although not as handy as the cataloging applications you can at least start tracking down where the disk space is going. With video you can probably just copy half a dozen files off and immediately free up many GB.
Note that this isn't just a matter of convenience. OSX makes lots of temporary files and is doing it all the time. If it can't find space for those files it can result in a serious drive crash and that could cost you several hundred dollars in recovery expenses. A Sig indicates, you need space just for computer operation. I feel the % recommendation is a bit vague since people use drives ranging from 10 - 1000 GB in size. My computer regularly uses 6GB of hard drive space for temporary files, and I like to leave wriggle room, so I usually leave at least 15-20GB. You can check the temporary file usage by looking at VM in Activity monitor.
As BDaqua observes, having a crowded drive also slows down your computer. If it has to hunt for nooks and crannies in which to place bits and pieces of bigger files that takes time. Normally one does not have to worry so much about fragmentation of files on a Mac, but your scenario of working with large files on a really crowded drive may be defying that generalization.