the images captured by screenshot captor are not going to be blurred -- there are only 2 possibilities:
1) either SC or MS Word/Excel are blurring when displaying them at less than 100% resolution
2) the files are being blurred when saving them in a lossy format (like jpg instead of png).
SO, the first step is to find out what is going on.
If you capture a screenshot and then view it in SC, with zoom set at 100%, does it look blurry?
Double click it in the thumbnail to open it up in your default viewer program, does it look blurry?
If you are saving as a jpg, try saving it as a png -- ie set your default image save format to png if you have previously changed it from that to jpg.