Windows 7 / 8 do limit the number of files you can "batch-work" with, after selecting them in Explorer and Right-Clicking for options.  The Standard Limit is set to 15 files. Selecting more than 15 files will remove options like "Print" from the context menu. To work with more than 15 files in batch mode, open your registry ( Run, "regedit" ) and go to

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer 

Create an new DWORD key with the Name MultipleInvokePromptMinimum and the Decimal Value of the Maximum Files you want to batch work with. I.e. 1000 (which could be too much or not enough - depending on your work and machine!)

And thats it. If you want to reset that option, just delete the created DWORD key again.