[wdh]

Ok recently my computer has been running fine and then it will suddenly slow right down and the programs i was running will beocme un responsive. ctrl alt delete will often return a black screen and then "logon process has failed to create the security options dialog"
Trying to shut down will take a very long time, occasionally a blue screen appears part the way through saying a message about checking new hardware and drivers although it goes before i have chance to read it fully.
Ive used programs like CCcleaner to clean up any temporary files etc as well as stopped a few processes and the sidebar from starting.
I also noticed that when the slow down happens if i open my kaspersky security centre, at the bottom of the window it usually says how much its scanend as well as number of viruses etc its found. But when the ocmputer is running slow they all read 0, not sure if this is a problem or if its just because its running to slow to display.

As for the computer its running Vista home premium x64 with service pack 2.
Computer has
AMD 9650 quad core processor
4GB Ram

Any help much appreciated