T-SQL (SS2K8) :: Identifying Potential Duplicate Records In A Given Table?

any useful SQL Queries that might be used to identify lists of potential duplicate records in a table?

For example I have Client Database that includes a table dbo.Clients. This table contains various columns which could be used to identify possible duplicate records, such as Surname | Forenames | DateOfBirth | NINumber | PostalCode etc. . The data contained in these columns is not always exactly the same due to differences caused by user data entry; so some records may have missing data from some of the columns and there could be spelling differences too. Like the following examples:

1 | Smith | John Raymond | NULL | NI990946B | SW12 8TQ
2 | Smith | John | 06/03/1967 | NULL | SW12 8TQ
3 | Smith | Jon Raymond | 06/03/1967 | NI 99 09 46 B | SW12 8TQ

The problem is that whilst it is easy for a human being to review these 3 entries and conclude that they are most likely the same Client entered in to the database 3 times; I cannot find a reliable way of identifying them using a SQL Query.

I've considered using some sort of concatenation to a new column, minus white space and then using a "WHERE column_name LIKE pattern" query, but so far I can't get anything to work well enough. Fuzzy Logic maybe?

the results would produce a grid something like this for the example above:

ID | Surname | Forenames | DuplicateID | DupSurname | DupForenames
1 | Smith | John Raymond | 2 | Smith | John
1 | Smith | John Raymond | 3 | Smith | Jon Raymond
9 | Brown | Peter David | 343 | Brown | Pete D
next batch of duplicates etc etc . . . .