i have a 70 mage, i havent played him in a year and a half.

Mages can easily be the most powerful class if you play them right. But also die the fastest. However, there is some major fun to be had. Theres nothing like just 3 shotting people from 40 yards away. Fire is what i chose, but its because i love pur raw damage. Ice is more defensive, but can also cause major damage. Either way mages have good aoe (area of effect spells) which are used to handle multiple eniemies. thats why mages are crucial in dungeons (that and food and water).
Mages can also teleport, and if your ice you can summon a beast for a a little while.

The security is based on your account, not the software. You can install it on 100 computer, but you can only login on one of them at any given time. Kind of a nice side effect of MMO’s

As for logging in on any PC with the game, that’s true if you and the install are the same with respect to the expansion. If you buddy has a second computer with The Burning Crusade installed, and you don’t buy it, you can’t play your account on his PC. Vice versa is also true.

If you want a very powerful solo class with distance attacks, try Warlock. I have a few 70’s, but I always seem to enjoy playing my lock the best.

Frost Mages are fun. They have a lot of utility.

They can Ice Block (fully cover themselves in ice and become invincible), Blink (teleport), use water pets (they shoot ice bolts), turn Invisible, create food and drinks for other party members, and even create portals to visit other cities.

You can also AOE (Area of effect) grind mages to a 70 very quickly. So they're fast levelers.

Asides from a mage, I would recommend a Warlock or Druid as a ranged attacker. If you consider yourself mostly playing PVE a Hunter would also be a great option.

Mages are regularly beaten by Warlocks and Rogues in PVE and an average class in PVP. You are mainly there for crowd control (sheeping linked enemies) and food/water spells for other classes. Before I quit and the food table spell had been patched, I saw many Mages being phased out of endgame raids in favour of other Damage Dealers.

Actually theres a limit of 50 chars per account. (Most people never make that many so the assume its unlimited, but then again i'm a freak).

Nope same key is fine.

No, yu use both spells, but yur talents will determine which will be stronger in certain aspects as yu get to be high level.

and I recomend Druid!