You can have a virus scanner without knowing about it.
So, open My Computer, Control Panel, Add/Remove Programs and check if
something like Anti-Virus Software is installed. If yes and you do not need
it, just uninstall it.
Next, if the problem is not solved, click Start, and check what is in the
Start-up section.
Next, click Start - Run, and type msconfig. Click the Startup tab, and look
if a scanner is included. If yes, uncheck the box, click OK and restart the
computer.
Or, if you have a Scanner, run it to check if your system has a virus or
worm...

And another solution (if there is a Scanner) - Maybe you have macros in your
files, the program will not allow you to save them, if Macro Protetion is
turned on.

--
Marin Kostov
Microsoft Office XP Master Instructor