So a customer asked me yesterday:
"How can I search all my DTS packages in SQL 2000 for certain field/table names? Peoplesoft patches sometimes change these at the schema level."
Answer: You can't, using any native SQL Server utility. The best you can do is save the DTS packages as a Visual Basic File (.bas or .txt) and either aggregate them or index them via some other utility.
Alternative Answer: DTS Compare from www.red-gate.com might do it, but I have not tested it.