i tried running the command over a linked server; basically i tried changing the last command to a 4 part command:
EXEC linkedservername.master..xp_regread 'HKEY_LOCAL_MACHINE', @inst, @inst1
got this error:
SOFTWARE\Microsoft\Microsoft SQL Server\SQLEXPRESS\MSSQLServer\SuperSocketNetLib\Tcp\\\\////TcpPort
Msg 7411, Level 16, State 1, Line 43
Server 'db1' is not configured for RPC.
maybe if RPC was enabled for the server, but i dunno...it's getting out of my area of knwoledge.
i think you'll have to do this in a programming language, or use RegEdit to connect to the remote machines using your domain credentials manually.
you could also try SQLRecon.exe, which scans a network for servers and reports back a lot of information, but it is not possible via a linked server.
Lowell