Improving slow queries. Slow query log attached
One area that stands out is the way you are accessing the BillDetails table. All queries appear to be using MONTH and YEAR operators on BillDate. For example:

SELECT SUM(GROSSAMOUNT) FROM BILLDETAILS WHERE MONTH(BILLDATE) = 8 AND YEAR(BILLDATE) = 2011;


This approach requires accessing every record in BillDetails. A better approach would be to index BillDate and query as follows:

SELECT SUM(GROSSAMOUNT) FROM BILLDETAILS WHERE BILLDATE BETWEEN '2011-08-01' AND '2011-08-31';


Looks like you don't have much data in there at the moment (1373 rows) so the difference in the above will be minimal at the moment, more significant when the volume grows.