I was just wondering,can you play another game,and still keep your old one,good for fixing mistakes,or having better character.I took a mage,and now cannot use the better armors and weapons.Sob.

Yes you can.
create a new avatar by typing the name.
Once you set it up you can restart the whole thing. Your saved games will be bound to the new character so each avatar has his own saved games.
i usually take a backup of my saved games folder every week :)
also save before entering and before exiting a new level. when you mess up something you don't have to fully replay the whole game.
I'm playing an archer atm with light combat arts. Works great so far :)
Earlier i've made a heavy combat arts avatar which was unbeatable :)

I take it you mean the uroks right?
Champion , devastator and hurler?
I've planted a few frosttowers and some archertowers alongside the riverbed . You can activate the dwarf monument ansd mine the stone there.
In between waves of trolls i ran to the ice elemental nodes to finish them off.
I draw back when trolls come again just before my towers.
I put my stats generally in :
+2 strength
+1 stamina
+1 dex
+1 agility
the following level
+1strength
+2stamina
+1 dex
+1 agility
I don't need a lot of intelligence for my occasional warcry/berserk spell
These stats benefit from the armor and rings a bit so i haven't had a problem with them.

I just finished the original campaign with a White Magic specialist (with a little light combat arts I took on the side at the beginning to be able to use a few extra early weapons and armor). Are you making full use of your heroes in the Southern Windwalls? Did you pick up the prince and the white wolf as "NPCs" to be extra cannon fodder? The necromancers in that area didn't give me too much trouble. Ignore any undead they summon and concentrate on knocking out the spellcasters, then mop up the undead. Try to draw them out a few at a time.
I actually highly recommend White Magic for the healing spells (your priest heroes aren't always very smart in using their abilities and don't seem to be very well-designed), the Hallow spell (takes out undead and Blades), Aura of Fast Walking, and Aura of Fast Fighting.

this is better balanced in Bow , you'll find a lot of priest with good auras. Fast walking , auto heal , slow fighting (NMY's) , fast fighting (yourself)
I usually am quite happy with blessing :)
i'm planning on replaying this with ice/fire mage.
I heard they kick ass.