Make sure that you have some of that extra memory allocated to the digital audio program you're using. Memory allocation is set differently from one program to the next, but the majority of them are flexible and allow you to make changes. On the Mac you can do it simply by clicking once on the program to select it, then go up to the File Menu and choose "Get Info" (or Command-I). You should have some options for "Memory" in this window, depending on what system you're using, and you should increase the "Preferred Size" a bit. The amount to increase depends on how much total memory you have in your computer, but you should never set the preferred size to more than half of the total memory available, because your computer's System will need some memory. Also, if you're using Pro Tools, add more memory to "DAE" (found in the DAE Folder inside your System Folder) rather than to the Pro Tools application itself.