This is a very common question:
CodeProject Quick Answers for "Crystal Reports Login Credentials"
Basically you need to program to set the login information so that it won't prompt.
Dim rd As ReportDocument
rd = New ReportDocument
Dim dt As DataTable = DataAdaptor.GetDataTable(sql)
dt.TableName = "yourtable"
Note: This code was taken from Member 2965545
]'s answer to this question:
Crystal Report asks for Login Credentials