To check Proxy table:

1> use DBNAME
2> go
3> select name from sysobjects where type = 'U' and (sysstat2 & 1024) = 1024
4> go

or

1> use DBNAME
2> go
3> sp_helpobjectdef
4> go

To check external logins:

1> sp_helpexternlogin
2> go