Windows partition update stalled

Hi, have a Microsoft partition on my Macbook just for the reason to maintain a bookkeeping program which is unavailable for my Mac (why else would I need it??). Now, it has now been keeping updating ("update no. 28 of 33") and has been standing like that for past couple of hours. I'm afraid to restart the whole partition for fear of loosing important material on that part of my HD. What can I do?? Thanx for any good advice!