SpaceTime Mobile has released a free scientific calculator for Windows Mobile and Palrm devices as well as Windows systems. If you find that the built-in calculator is holding you back and not providing all the functions you need, this alternative offers an innovative memory system to store and recall answers.
Note: MyCalculator is free for individual use. You will need to contact Space Time Mobile to obtain a commercial license if using it for business purposes.
Source: Pocket PC Thoughts