The only correction to Tony's explaination is that in the key of "C", the II chord of teh scale is always a minor chord, so to be more precise ... it's a "Lowered D minor chord with a raised, or sharped 9th"
The Roman numerals depicting minor intervals should be in lower case also.
eg:
I(Maj)
ii(min)
iii(min)
IV(Maj)
V(Maj)
vi(min)
vii(this chord is actually diminished, but I don't know the right symbol to type on this keyboard!)
****
...that will bring uis back to Do, oh, oh, oh ..... (get it?)