Jaikoz can only use the memory that has been allocated to it, by default this is 800MB, so it doesnt have access to the other 15GB you have. So I expect you havent modified the memory settings please see:
http://www.jthink.net/jaikoz/jsp/help/windows/help.html#MemoryManagement
You can check you have done it correctly easily, when you start Jaikoz the Jaikoz Console Window says something like
Nov 29, 2011 1:11:05 PM: INFO: Jaikoz has been configured with minimum heap memory of 150 mb, maximum heap memory of 795 mb and maximum permanent memory of 216 mb
The Preferences/Local Correct/Year Correct/What should the Year contain option defines what running Local Correct Year will do, so you need to make sure you run this before saving your songs. Your songs will be saved with whatever is displayed on screen.
on startup, you should expect maximum heap memory to be about the same as the new figure you have set.