I have a single threaded application that runs on a machine with a quad core processor. The scheduled tasks that run VB.NET forms are too slow.

I am new to multi threading and parallel computing. If you have a single threaded application that runs on a server with a multi core processor then does the application only ever use one of the processors? What happens if you have multiple scheduled tasks and multiple instances are in memory at the same time?

I have read this question on Stackoverflow: http://stackoverflow.com/questions/607775/how-to-write-net-applications-that-utilize-multi-core-processors, but I am still not clear.