sedona :
What if I'm opening Firefox browser playing Youtube video, then run a virus scan software, then play a DVD on Windows Media Player, then run a stock market trading software with real-time stock quotes coming into my stock charts, etc. How do I check which core or which thread is doing what? Is it possible that all these tasks are running on only 1 core because of the way the software is written?
First of all, all applications run on threads, which then handle it to the core.
Threads can be translated to process(more or less).
a dual core with hyperthreading have 4 threads, and a quad core without hyperthreading have 4 threads.
A programmer cannot decide which threads will be used to his process, he can decide how many and how important they are.
Windows will assign each process to a thread. A thread can only handle 1 process at a time.
As I dont know which 2 processors your are looking at, I cannot say which one will handle all those task best.