spreadem -
Dual processors will deliver increased throughput IF you have at least two heavy CPU consuming processes running on your machine or you've got one heavy CPU consuming program that is multi-threaded and does some parallel processing. Otherwise, it's not going to do much for you running Word or Excel or primative database processing.
However, contrary to someone's earlier post - most realtime datafeed/charting software is already multi-threaded and/or multi-process based.
Examples - the Qcharts datafeed runs in its own thread of operation while any software that uses runs in one or more separate threads. I believe both eSignal and DTN.iq run data managers in processes separate from any program that uses their datafeed.
In each of these cases, if your particular usage produces high CPU utilization, then dual processors would probably deliver a decent incremental performance boost. Of course, if you're memory, disk, or network bound instead or multi-threaded code uses poorly designed synchronization granularity, then you've got a different situation.
Similarly, if you're doing database-oriented analysis/mining, SQL Server is internally multi-threaded but MS Access isn't. So assuming you have a large memory footprint that could be used to cache a significant portion of the database so that your database analysis was primarily CPU bound rather than disk bound and especially if your analysis software issued multiple simultaneous requests at a time, then you could see performance improvement from dual processors when using SQL Server but not if you used Access.
Also, note that while commercial realtime datafeed/charting apps are multi-threaded and/or multi-processed and therefore could benefit from multi-processors, most commercial system optimization and backtesting software (or the optimization and backtesting functions within commercial charting apps) is single-threaded due to data and processing result dependencies and would realize little or no benefit from multiple processors.
Of course, if you plan to write your own optimization/backtesting software and are skilled in multi-threading, you could benefit from multi-processors.
However, unless you expect to be heavily CPU bound in your processing (and typical end-user applications are not), worrying about single vs. multiple processor configs is moot.