Thread question

Greetings,

What would cause a thread to exit with a -1 ?

The thread 0xFFFB5059 has exited with code 0 (0x0).
The thread 0xFFFC6661 has exited with code -1 (0xFFFFFFFF).
The thread 0xFFFB4AA5 has exited with code 0 (0x0).

How can i identify which thread is performing which functions ?

Why are there 6 threads when executing my SDL app in Win2k and 

only 3 when in Win98 ?

Where can i learn more about threads in general ?

Thank you.

-dv