At least for my Office2010, executable name for Word is "WINWORD.EXE", not "word.exe", and "POWERPNT.EXE" not "powerpoint.exe". Did you confirm these executable names for your Office?
Usually the programs belonging to the MS Office suite, don't require to add the appropriate path to the link. In my case for example, the following options work well:
For Word: LeftMouseUpAction=["WINWORD.EXE"]
For PowerPoint: LeftMouseUpAction=["POWERPNT.EXE"]
For Excel: LeftMouseUpAction=["EXCEL.EXE"]
As you see, just the file of Excel is named Excel.exe. The name of the file of Word is WinWord.exe and that of the PowerPoint is PowerPnt.exe.