hi Manisha,
This would be Generally carried out by N/W Admin. who has to create alias for the Server in DNS. Here are some of the steps which you may consider.
1 -> Create a DNS Alias record for the service desk server: Eg: if the server name is ServiceDesk then create a alias record under domain in DNS as say "abc" and make sure this points to ServiceDesk server. Now the alias URL will be
http://abc
2-> On IIS Server, on the properties tab, under the Home Directory, make sure the option "when connecting to this resource..." points to the following location C:\Program Files\CA\Unicenter ServicePlus ServiceDesk\bopcfg\www\wwwroot
3-> Make sure that you have Scripts and Executables as the permissions.
4-> Make sure that you have the default document enabled, and have pdmweb.exe as a default document.
5-> Stop and restart the IIS server.
Note: These above steps where carried out in older version., IIS Setting would change based on Version of IIS.
Hence Recommendation would be to consult N/W admin.
~vinod..