Not sure what the technical term is, but we're having problems with our PC 'stalling' after being left idle for more than a few minutes.

Basically the routine goes like this: start up pc no worries, can surf the net & load programs all quickly and as it should be, leave the pc at idle for 5 minutes (with programs running or not, it makes no difference) then on returning to PC, the mouse pointer may move a little, but nothing opens / moves / actions and we have lost control.

While its stuck like this, I can hear the HDD whirring a little, but its so stuck that even a CTRL+ALT+DELETE does nothing, only solution seems to be restarting pc. On restart we get the whole 'disk needs checking', this is our routine as its been for a week or too.

Have tried multiple virus checks, ccleaner, disk defrag & clean up.

I checked the event log, and found this:

anyone know what to make of the error message:
"The device, \Device\Harddisk1\D, is not ready for access yet."

Source: Disk
Event ID: 15

and another error message:
"The Cardex service failed to start due to the following error:
Cannot create a file when that file already exists."

Source: Service control manager
Event ID: 7000

Have tried a google with no luck, so any help much appreciated.

Machine is:
Windows XP home, service pack 3
AMD Athlon XP 2700+
2.17GHz, 2.00GB of Ram