After installing Reporting Services on a Windows 2003 Server SP1 Box, everything seems to be ok, but when i browse to the Reports website: http://localhost/Reports i've got the following error message: HTTP status 401: Access Denied.
After some Google search i found that this is not a problem related to MS Reporting Servers, but it's an issue related to Windows 2003 Service Pack 1.
If you have this problem, and you have a box with Windows 2003 with SP1, follow these steps to fix it.
1.Click Start, click Run, type regedit, and then click OK.
2.In Registry Editor, locate and then click the following registry key:
3.Right-click Lsa, point to New, and then click DWORD Value.
4.Type DisableLoopbackCheck, and then press ENTER.
5.Right-click DisableLoopbackCheck, and then click Modify.
6.In the Value data box, type 1, and then click OK.
7.Quit Registry Editor, and then restart your computer.
You can find more details here: http://support.microsoft.com/kb/896861/