There is a nasty PC virus going round at the moment, and it is affecting millions of PC running Windows. You can read more about it here:http://news.bbc.co.uk/1/hi/technology/7832652.stm
Make sure you do the following:
1) Run "Windows Update" and install all the Windows fixes you can. This problem was "fixed" by Microsoft in October last year so if you are up to date with Windows Update you should be covered.
2) If you have not got any anti virus software then install one (there are plenty of free AV products around).
Download the lates virus "update" from your company then run the anti virus.
If possible set your anti virus to run every day at the same time.
If you DONT do these things then you are leaving your PC wide open for a serious attack from this virus which may result in a complete reinstall of windows.