I was installing a Dual Tier Team Foundation Server 2008 at a clients today and got a problem that when installing the Application Tier (AT) I entered the name of the Data Tier server (DT) and it said the server could not be found.
Unlike TFS 2005, 2008 does not require you to to do a separate install on the DT to create the empty DBs, so I assumed it was just a connectivity problem. However there was none to be found, so I checked the detailed TFS install error log and saw I had a TS220066 error that also mentioned SQLRS - I guessed at a reporting services issue.
I turns out, stupidly, I had forgotten install SQL Reporting Services on the AT - after all I have previously posted about following the walk-thru for the install!
Once this was installed all was OK; so if you cannot see the DT during the AT install it may not be the remote connectivity issues the dialog says, check the error for more details.