How do I leverage the power of my desktop from my laptop?

"Short answer: No. Not in a general purpose way.
You can use the desktop via VNC or Remote Desktop, but you said you don't want that. You want the work to seemlessly move to the desktop when the laptop hits 100% CPU usage. You may be able to find specific applications that can do this, but there is no general purpose solution for doing so.

The reason for this is the difficulty in moving work to another machine. There is a lot of complexity involved in moving to different hardware and memory. Unless the program is made to handle this complexity, it isn't possible to make it work."

"The only seamless solution in existence is distributed processing, of which the world's greatest example is the Google internal network. However, this requires specialized software and is not supported by any utility I know.

You also refer to clustering, which is the same : only used by large and specialized software products, for example database servers like SQL Server or Oracle.

The answer is then that you can't distribute the workload automatically. The most you can do is share your hard disks between the two computers, and launch your heavy tasks on the desktop thru Remote Desktop or VNC. However, please take note that while large files are transferring between the laptop and the desktop, both machines will most likely be too occupied for other tasks."