The 2handed axe of winterun i got from doing the main quest had soul tap on it, so i just disenchanted that so i can enchant it onto other weapons i use.
Dont know if thats just a random weapon when you get it as a reward or not.
Unless it's a different axe, I've had the Winterrun axe on two different characters, and both times it had a frost damage enchant. It may vary though ... I was amazed today to be given the Flame Atronach summon today in order to prove myself to gain entry to the College of Mages instead of the dodgy flame spell I got on my first character.
Personally I got an iron sword with Soul Trap on it for a character level 7, and then disenchanted it. Well worth c. 500 gold, but I was lucky with vendor loot I think, because it's a random table.