Graphs problem

Ok sci I have this problem - I have a Complete undirected Graph with "n" verticals but instead of a single edge between every two verticals there are two parallel edges. I need to find how many Spanning Trees the graph has.

My question, let's say it's a normal complete undirected graph. How do I find how many spanning trees it has? Is it by recursion? If so than what is the first step to get the formula? Or better yet is there a formula at all? I don't remember coming across anything like that at all ever.
How do I choose the edges correctly to build up a tree?

Oh wait, is for the normal complete graph formula :
(n c 1)*(n-1 c 1)*(n-2 c 1)* ... *(2 c 1)*(1 c 1)  ?

Writing to you guys sure help me help myself.

Just want to know if my final answer is correct -
2^(n-1) *n!

If anybody knows the answer for the original question I'll be glad to know.

Any chance that after many steps it sums to:

2^n * [sum(i=1 to n): n!/(i-1)! * i^(n-i)]

?

x

wat