Hi and thank you both for your replies.
A system restore would be unpractical because the problem started a few weeks ago and as I don't use the options that often I wouldn't know when it actually started. Plus I have installed a few things since then and updated my drivers so I wouldn't want to uninstall all that.
kesume as this file contains kernel functions I recon it's fairly important so it should disrupt other processes. I checked and Word did stop working for some time yesterday with a ntdll.dll error (see attachment) although I did get another error with a faulty mso.dll. Any idea on what I should do to repair this .dll?
I also have a much bigger problem related to my external hard drive which is described accurately in this thread BSOD when transfering Large files to external HD
(I have the same error message and same external hdd) but it's a different problem as far as I can tell and I'm just mentioning it in case anyone makes a connection to this dll as the solution hasn't worked for me.
Please let me know your suggestions.