Ok, thank you for reporting your problem.
A few questions/things to check;
a) In the status notification area of the taskbar (bottom right on your screen where you have the clock, speaker volume etc), can you see the Notifybox icon? I.e. is Notifybox running on your computer? You can also check this in Windows task manager, you should have a process running called “Notifybox.exe”. If the answer is no, then go to the start menu -> Ifront Notifybox and start the application. Then you should get Notifybox icon in the notification area of the taskbar.
b) If you have a Notification icon in the notification area of the taskbar, right click on it and select ‘Properties’. Make sure in the ‘Account’ tab that you have selected the correct path to your main Dropbox folder (Dropbox path). Also check that you have selected a “Folder to watch and monitor”. In the free version there is only files in this folder that will be monitored. Also check that the checkbox “Start Notifybox when Windows starts” is checked so the application auto-start the next time you restart your computer.
c) When the application is running and the correct folders have been defined you should be able to check-out and check-in. Go to the folder you selected as the “Folder to watch and monitor”. Drop a Word or Excel file in this folder. It should then as normal be synchronized by Dropbox. Then try to open the same file again by double-clicking on it, or open it from within Word or Excel. Do you then get a message to check-out?
d) If not, open the Notifybox application again by selecting ‘Properties’ after right-click on the Notifybox icon in the taskbar. Go to the ‘Event log’ tab. Can you here see anything else then the message that Notifybox has started? I.e. has the application recognized that any files has been created or updated etc? If not, are you sure that you have selected the correct path to the Dropbox folder under the ‘Account tab’?
e) And – if it still doesn’t work - what version of MS Office are you using? What Windows version are you using?