Blurb from their site:
Process Lasso is a unique new technology intended to automatically adjust the allocation of CPU cycles so that system responsiveness is improved in high-load situations. It does this by dynamically temporarily lowering the priorities of processes that are consuming too many CPU cycles, there-by giving other processes a chance to run if they are in need. This is useful for both single and multi-core processors. No longer will a single process, even at normal priority, be able to bring your system to a virtual stall.
In addition, Process Lasso offers capabilities such as default process priorities, termination of disallowed processes, and logging of processes executed.
For Windows 2000, XP, 2003, and Vista.
http://www.bitsum.com/prosuper.asp