Thanks for ur all support,

Reason of the problem :
1) The user automatically create a IUSR_machinename user. This user is a Internet User, guest created by default by IIS5.0.
2) When try to login to the SQL Server 2000 DB it will says login fail as user IUSR_machinename.

To solve this problem :
1) Go to the SQL server 2000 DB.
2) Click the DB which has error.
3) Go to the user
4) Add new login user
5) Create IUSR_machinename.

Then all the problem is solved

Thank u