Merge Report / Find Duplicates ?!?

I'm really not even sure if this is possible, but I've have always received great advice from people in the past, so here it goes.

I have a report with 600 rows and 2 columns that includes the company name and contact name only. I have another report with 5000 rows that includes company name, contact name, address, phone number, fax number, and additonal data. The 600 companies are located somewhere on the 5000-row list.

I need to take the 600-row list and locate the addresses for those companies on the 5000 list. Is there any way to do a merge/locate of the two reports without manually going through each row?

I don't know...add a column to the 5000 report, import the 600-report and find duplicate? I have no idea, but if anyone has any suggestions, it would be a HUGE help. Thanks!!!!!