My daughter is 16yrs. old, and started her very 1st. period july 2005.
Since she has started, the periods have not been regular at all. They
come on average 2 times monthly and last 5 days or they come atleast a
week early. They start with a dark brown color,and then turn to a
normal red color...Could this be a serious problem or normal for
beginners? Thankyou(we have seen a primary doc,and he said this is
normal in the beginning)

from http://www.webmd.com/hw/healthy_women/tn9933.asp
"Normal Menstrual Cycle
Menarche and the Teenage Menstrual Cycle

Long, heavy periods are fairly common during the teen years. The
hormone (endocrine) system is still maturing, and progesterone levels
aren't always high enough during regular cycles to help the uterine
lining (endometrium) break down. When the endometrium has built up for
too long, heavy menstrual bleeding follows. This type of bleeding
usually gets better on its own, without treatment. However, see a
health professional for menstrual bleeding that lasts longer than 7
days or for cycles that are shorter than 21 days or longer than 42
days."

fron http://www.emedicine.com/ped/topic628.htm
"Irregular and anovulatory cycles may persist for as long as 1-5 years
after the onset of menstrual periods."

The previous comment is true in part. Your daughters' cycle is still
maturing.  How long it will take to settle down is anyones guess and
in a minority it never settles.  It is not a sign that there is
anything wrong.  It is a nuisance rather than anything else.  If the
problem becomes too much to put up with then the combined oral
contraceptive pill will regulate her cycle.
Regards,
prof10-ga