If you want to allow to certain users or groups to access on specific reports in SCCM 2007 with SQL Server Reporting services installed, follow these steps:
First create a AD Security group which will have permissions to browse SCCM SRS Reports. ex: SCCM_Report_access
Open SQL Server Management Studio and add this group in Security -> Logins.
In User Maping choose your SMS database on right side and click on public and db_datareader.
Next step is to allow SCCM_Report_access group to access on SCCM reports.
Open Web SCCM Reports : http://sccm/Reports/
Choose some link and click on Properties:
Click on Security:
Click on New Role Assigment:
Paste MYDOMAIN\SCCM_Report_access Group or user name field and choose Browser.
After that users members of SCCM_Report_access Group will have access to Hardware - General Reports.
If you want to deny access to specific report then you have modify permissions on that report explicitly.
To allow users to see reports you must assign Browser privileges to Security group or users starting from root (http://sccm/Reports/). With this action, because this permissions are inheritable all sub-links will have same permissions. If you don't want all reports to be seen by the users then you must modify permissions on each sub-link.