2000 Bonneville will not start

My 2000 Bonnie will not start. The car seemed fine on the way to work,
fluid
levels are OK. When turning it over, there is a loud clunking noise, and
it
seems sluggish when trying to turn over. I had a battery booster on it
earlier today, did not help or hurt anything. I want to try to hook it up
to
a vehicle soon (it's in a parking garage, which is why I tried the booster
first), but I was wondering if anything else may be causing the problem. I
gave it a little gas while trying to start it (which I know i probably
shouldn't do) and it stopped cranking at that point. Any help will be
appreciated.