Over the past month or so my laptop has been driving me slowly insane. It’s performance has been absolutely dire, particularly when trying to work under VMWare. I’ve spent many hours staring at the task manager looking for rogue processes that might explain the constant disk thrashing but to no avail. Process Explorer (one of the Sysinternals tools now owned by Microsoft) came to the rescue indicating that, for example, when running VMWare, 50% of the CPU was being used to handle hardware interrupts.
A quick Google suggested an issue whereby Windows steadily reduces the transfer mode on an IDE channel after six cumulative time-outs or CRC check failures until eventually it hits rock bottom speeds with PIO mode. Checking the device settings confirmed that this had happened or, alternatively, my primary hard disk has always been running in this mode. One suggested mechanism to reset the mode is to uninstall the driver and let Windows reinstall it on reboot. I’m now back in Ultra DMA Mode 5 and everything is zipping along nicely – even the reduction in noise level is noticeable!