well i just installed freebsd and i'm using gnome. by looking at the system monitor i can see that when i download something my user memory is being used (downloading a file using firefox 1.5). this memory is the ram right? well my question is why does this do that? is it supposed to? and what happens if i download a file that is bigger than my memory and my swap? shouldn't files be downloading straight to my harddrive, instead of being stored in my system memory?
last night i downloaded an iso file and this morning when i woke up my pc was froze....

Download the file to a specific location [folder or even the desktop] where you know for sure you have room for it.

Well firefox uses ram and so do other system resources.
It downloads to whatever folder you have instructed it to. I do it all the time without any problems.
Did you pay your heating bill on time?
Did it download the whole iso? Was there any error messages or any messages at all? Did you find out what froze your system?