If you have the files in a CSV, then you can put a column at the right and use a formula for =LEN(A1) or whatever the column in.

To import into SQL Server, you can use BCP.

http://msdn.microsoft.com/en-us/library/aa174646%28v=SQL.80%29.aspx

However this error is what it says it is. You are inserting more data into a field than the field has space for.