Visual Studio 2005 - Extract Rows From DataBase - Replace Fields - Insert Into Another Table

I work with Visual studio 2005 and Sql server data base. I extract 1 million rows from a database and I put the rows in a Sql table. With a simple direct extraction, in a few minutes I complete the operation:

Dim cmd As New SqlCommand(query, cnSql)
cmd.ExecuteNonQuery()
cmd.Dispose().

But, if I must select and modify some fields between extraction and introduction, it takes a lot of time!
I work in this way. I extract rows from Dbase, Table1, and I put all into a Collection using dataReader:

Dim cmd As New SqlCommand(query, cnSql)
Dim coll As New Collection
coll.Clear()
Dim dr As SqlDataReader = cmd.ExecuteReader()
I replace some fields with the string "YES".
Dim toRepl As String = ""
If dr.HasRows Then
Do While dr.Read
toRepl = dr(5).ToString
If Len(toRepl) <= 3 Then ToRepl = "YES"
collPrel.Add(dr(0).ToString)
collPrel.Add(dr(1).ToString)
.................. ..............
collPrel.Add(toRepl)
collCount = collCount + 1
Loop
End If
dr.Close()
cmd.Dispose()
Now, I insert all into a SQL Table2:
Dim a As String = "", b As String = "", c As String = "" etc.
For i = 1 To collPrel.Count Step 6
a = collPrel.Item(i).ToString
b = collPrel.Item(i + 1).ToString
.............. ...............
f = collPrel.Item(i + 5).ToString
queryIns = "INSERT INTO Tab (name, adress, etc)
VALUES ('" & a & "', '" & b & "', '" & c & "', etc. )
Dim cmdIns As New SqlCommand(queryIns, cnSql)
cmdIns.CommandTimeout = 600
cmdIns.ExecuteNonQuery()
cmdIns.Dispose()
Next

This way to work goes right but it is necessary a lot of time for completing the operation.