Hi Katie, some of those levels are really hard!  If you look at the top of this page you will see forums.  Check the Diner Dash 2 forum and you should be able to find help on each level you get stuck on.  It really helped me a lot.   While checking on the forums you might want to pop into the Lounge.  It's a place where we just have discussions.  Lot's of wonderful people there!  Hope you will join us! 
 
Some general tips:  Try to seat customers clothing colors to seats.  Be careful where you seat people.  Especially the cell phone addicts.
When you see the closed sign go up and you have enough clean tables for the customers in line don't clean off any more.  Save as many to clear off as you can at the end.   This will give you a lot of extra points.   Seat business women as soon as you can.  Don't sit the cell phone addicts by them!  Cell phone addicts needed to be seated quickly.  The bookworms don't mind waiting in line a little longer.   On the levels with the podium you can keep hitting the little heart on there as much as you want and you can leave bookworms till last.   Most of all:  Have fun!   Candy

Did the game install fully?  Did you see a box come up that said continue or run?  If you didn't  look at the bottom of your desktop and see if there is a new icon there.  Double click on it and click on continue.   Also when you went to download the game did you see a yellow bar on the top of the page.   This is a security bar and sometimes you have to click on it.   Hope you get it to work soon!