If the message is like this one, its a virus:
http://static.commentcamarche.net/en...message-s-.png
Its a conflict with the installer. NSIS is a installer commonly used to install programs. You have a conflict between windows installer and the NSIS installer used maybe in the nVidia driver installation program you used (or anyone you used)
I could help with remote access to the computer if you want
If the message is like this one, its a virus:
http://static.commentcamarche.net/en...message-s-.png
Hmm but it's happening on any file I try, including ones I know work (as I have previously installed them).
Not a message like that, don't have a screen shot but it seems legit. Says exactly how I quoted it!