The Replace() function doesn't work on Text and NText fields in SQL 2000. You have to use SubString() and/or Stuff() and cycle through the column or variable changing the first found instance of the pattern until they are all accounted for.

Declare

@Table Table (Myfield text not null)

Insert

Into @Table

<SELECTReplicate('1236547890', 10000)

Update

@Table

Set MyField = Replace(MyField, '654', '456')---------------------------------------------------

Msg 8116, Level 16, State 1, Line 6

Argument data type text is invalid for argument 1 of replace function.