Device Activation Error

Question

Hi,
Iam using Sql 2000 as Back End
Iam attaching Database at runtime.
I have used foll code to attach database:
vConn.ConnectionString = "Data source=Localhost;uid=" + UID + ";pwd=" + UPWD + ";database=Demo;AttachDbFileName=|DataDirectory|Demo.MDF;";
But while running code it giving me foll error:
Device activation error. The physical file name 'C:\Documents and Settings\admin\Desktop\Demo\Demo\bin\Debug\Demo.MDF' may be incorrect.
Could not attach database 'Demo' to file 'C:\Documents and Settings\admin\Desktop\Demo\Demo\bin\Debug\Demo.MDF'.
 
Plz help me out!