1) Distributor_admin -

Replication Linked server login ,created while configuring Replication

2) Excelserver

Its User login ,asked who created it .

3) NETSOL\backup

4) NETSOL\Cluster

5) NETSOLetsol_admin

6) NT AUTHORITY\SYSTEM

7) NT SERVICE\ClusSvc

These all are Windows logins,Contact your System Admin