Welcome to JavaRanch! Adjusting JVM memory usage parameters isn't really beginner stuff. The intermediate forum might be a better place for this inquiry. But, since you've seemd to mention that you want a JCreator specific solution, I'm moving this to the IDEs and Other Tools forum...
Typically, this involves adjusting the JVM options as Dirk mentioned above. However, JCreator is a native Windows Application so it is not so cut and dry. It is unlikely that anyone in this forum is going to be able to help so I recommend you send an email to firstname.lastname@example.org detailing the error that you are getting.
Joined: Dec 10, 2001
To me it's not completely clear whether this problem is to do with adjusting JVM settings for Java applications that are run through JCreator, or if this is to do with a problem of an improperly running JCreator. I'd guess that it's the first. Should that be the case, then the solution might differ depending on the version of JCreator in use. But I'm pretty sure that this can be configured similarly for JCreator 2 and 3. For JCreator 3, you could go to Tools -> Options -> JDK Tools -> Select Run Application -> Select Default (or create new on by copying) -> Edit... -> On the Parameters tab, adjust things as you'd prefer. Then for details on specifying how much memory to allocate to the JVM, take a look at Sun's java tool documentation.