here is an example of something that works for me:

create table textstuff
(pk int not null primary key,
textcol text)
go

--insert statements

declare @int int
select @int=max(datalength(textcol)) from textstuff

select pk, checksum=checksum(substring(textcol,1, @int)) into holding from
textstuff order by 2

select pk, holding.checksum from holding,
(select checksum, test=count(checksum) from holding group by checksum having
count(checksum) >1) as a
where holding.checksum=a.checksum

rows which have identical checksums will show up here.