When am I using too much memory?

Like several posters, I deal with wav files resulting from sampling at 44.1KHz. I notice that Nero Wave Editor can somehow accommodate really large wav files without problems. For example, I can use Nero to work through files resulting from recording many minutes of sound.

On the other hand, if I try to read these files into Matlab I get into serious trouble. Is there any way that I can figure out when I am close to being maxed-out memory-wise so that I can adjust the size of the files that I want to work on?

Finally, does Nero Wave Editor do some sort of compression that allows it to work on large files (admittedly, this may be the wrong place to ask that question)?

Thanks.