could someone explain what the thaco is
and on the weapon speed factor?

you have icewind dale... read the manual.. if you don't have the manual, browse the disk, there's a copy in .PDF format. i think they even give you a copy of Adobe Acrobat so that you can read and print out your own instruction manual.
THAC0 is literally "To Hit Armor Class 0", which is a number on a 20 sided dice that needs to be rolled higher than to land a hit, so the lower the better. Speed factor has to do with wether you attack the enemy's first of they attack first each round. round? well, you may notice how spell casters sit around a few moments after being orderd to cast a spell?, they're waiting for the round next round to begin, and a fighter with a dagger has a better chance of hitting that enemy spellcaster before he gets his spell off.