ACCESS between serveral SQL-servers

I'v set up a new SQL6.5 server. The idea is to relieve our main server.
The problem is that I can't run a SP on the main server from the new server.

Ex: *fake data*

Insert into newserver exec mainserver.database..sp

this will generate:
Msg 18484, Level 14, State 1
Unable to connect to site 'newserver' because login failed

I've managed to add the newserver in mainserver.master..sysservers and the mainserver in newserver.master..sysservers

The way I see it I've got a problem with the users...??
This is all new to me so please help me!

Thanks:
BixHi, It's me again.
I solved my problem, and it was easy...
I guess that it was so easy that you guys didn't bother *s*

If anybody else get my problem, the answere lays in "Remote Servers" under the "Server" menu.
Register a remote server and map the logins...
and everything works like a dream!

Thanks!