viewing ssrs reports in another system

hi... to all..
i've developed one ssrs report in "sql server 2008 express with advance services"...

The virtual folder is not there in IIS .. ok it works fine ..

i.e http://mysystemname:8080/reportserver_sqlexpress it works good...

but the same thing i want to execute in another system .. with my system ip..
i.e http://my ip:8080/reportserver_sqlexpress the logon promt is appearing with uname and password..
i'm giving here my system uname and password..
after pressing ok..
the following error is displayed..

Reporting service error
The permissions granted to user 'mysystemname\Guest' are insufficient for performing this operation. (rsAccessDenied) Get Online Help

what to do...

please help me....

Is the machine in domain? What's RS service account? Did you connect with domain account? Assigned proper permission in RS for that user?