I am not aware of any behavioural problems with my desktop computer, which is running Windows XP Home SP3. Whilst idly trawling through its configuration, wondering what to tweak and subsequently regret, I noticed that several times an hour I am experiencing an event 51 as reported in the Event Viewer: An error was detected on device \Device\Harddisk1\D during a paging operation I have Googled this and it seems quite common - but what does it mean? My drive D is a CDROM reader & writer. I have run a disk check on the hard drive [C:] and it is clear. I also have an external hard disk [E:] via a USB connection.