How long did the test code as written take to run on your computer?

From the information you have given us so far it looks like the only answer is to get a modern computer with sufficient memory to allow using the memory to make the task faster. Many ways of making algorithms faster involve using more memory (which is fast) to avoid having to do as much disk I/O (which is slow). If your computer doesn't have enough memory then there may be no way to speed up the processing.

That said, if we knew why you are trying to do this search we may be able to suggest a better solution.