To modify the reports in MS Access 2007, you need to open the Stockroom application in MS Access 2007. Do this by opening MS Access 2007 and then selecting Open > and navigating to your Stockroom directory. Once there, select your Stockroom access db file, something like ITSTOCK7.accdb. The Stockroom application will open within MS Access. Select Tools > Database > Database Window from the ribbon to open the Access Navigation pane. It will appear along the right of the screen. There, select your report to modify. Modify the report in the Access environment. Once saved, you should be able to see the modifications when you select the report from the Stock report list in Stockroom (reached by selecting Reports > Stock from the ribbon).
If you add a customized report in Stockroom via MS Access, you are able to add it at the Customize Reports form in the Stockroom application (Tools > Customize > Reports). However, in order for this report to appear in your Stockroom report list (Report > Stock to open the Stockroom reports list), you need to open the Reports table in MS Access and find the Report ID for the new report. Then, you need to open the Modules table and find the Module ID value for your application (Stockroom). Then, you need to open the ModuleReports table and add a new record for the new report: to this new record, add the ReportID and ModuleID values for the new report. After doing this, the new report should be listed in the Stock Report list in Stockroom (which you reach by selecting Report > Stock).
Your report button should not be grayed out for the Stock or Inventory reports, but it is grayed out for the Check In-Out Reports, since they are not available in Stockroom.