startup disk?
 

Of course, I've got 2 internals & one external (+1 for backup.)

Unfortunately the Java on Mac OSX is as inefficient as the windoes version re: memory. If the programs been on for a no. of days then the amount of virtual memory (VM) it eats up grows. All OSX programs use VM which means temporarily storing memory on the hdd. Quitting the program will regain all space lost to VM. There's other techniques you can use for reducing VM growth such as: Not having much more than 2,000 shares. Not having too many incomplete files. Keeping only one LW window open at a time (monitor, library & connections) ... only opening when needed. Hiding LW in the dock whilst you're not at the computer. Deleting old search results if there's many. All these things can help reduce VM build up.

Do you have LW set for iTunes auto-import? Once imported then you can delete them from LW's downld folder. But just check to be sure all audio files were imported. That will help to stop too much space being eaten up by dual copies of files.

BTW on my computer, I use partitioned HDD's. I don't save files to the OSX system partition (startup disk.)

I've installed ram but never an internal HDD on a mac. I wouldn't recommend it if you're not sure what you're doing. And does your computer have another HDD slot? Here's a starting point http://www.apple.com/support/diy/ You choose your computer model & instructions on installing ata hdd's, etc. will display. Another alternative is an external firewire drive (I'd recommend Firewire 800 over 400. I've had issues with having my iTunes library on an external 400.) Space is a premium on the OSX startup disk as all programs use VM whilst they're open which takes up HDD space.

BTW I have 3 startup drives on mine. OSX, OS 9 (different partitions), & another OSX on a different hdd. The 2nd OSX gives me alternatives for maintenance purposes, etc. I also keep as many as possible programs installed on an Applications partition. But this is a very personalised setup.