Last updated: 23 March 2008
It is a possibility that a slowdown in disk read/write could be due to the data transfer mode for the hard drive has been changed from from the fast DMA (Direct Memory Access) mode to the slow PIO (Programmed Input/Output) mode.
This article tells you how to check the Transfer Mode setting for your hard drive/s and/or optical drives:
Note this content in that article:
Windows XP only
Windows XP reverts to PIO mode after several attempts to use DMA mode have failed. If this had happened, Windows XP will not return to DMA mode even if you instruct it to do so. Microsoft considers this a safeguard, but many users find this feature confusing. In order to manually reset the access mode, you can uninstall the drive and reboot. Windows will detect the drive at the first boot and use it. You can then set the access mode to DMA, and Windows will use that setting. Of course, if there is a real problem using DMA mode, Windows will revert to PIO mode again.
If a device is running in PIO mode, you must determine what caused that - one likely candidate is cabling for power or data - if cabling causes intermittent faults or lower voltages than should be the case, this can lead to slowdown in data transfer, with the operating system then reverting to PIO mode. Also If you are using a 40 wire ATA/IDE cable instead of an 80 wire cable, the 'cross-talk' (electrical interference) between wires can lead to slow-down in data transfer and then reversion to PIO mode. Other causes can exist.
You might be interested in some of the other articles on my site: www.pcug.org.au/boesen/index.htm