[krunchyfrogg]

It doesn't affect your number of attacks at all. What Speed Factor does is determine when you'll attack.

In AD&D 2nd edition (what the BG series is based on), you act in initiative order. Initiative is determined as follows:

1) All participants roll 1d20.
2) Your Speed Factor (or Casting Time, when casting a spell) is added to this number.
3) Your Dexterity Bonus is subtracted from this number.
4) All participants then go in order, from lowest to highest.

This means that weapons with a lower speed factor will be swung faster, and you'll hit your enemies (hopefully) sooner than they'll hit you.

Attacks/round are determined by your Fighter (or Paladin/Ranger) level. Otherwise, you get only one attack per round (unless using a weapon that grants you more attacks).