If anybody on the list has problems with a Win XP system that has become
painfully slow despite virus and spyware removal, the following tips may 
help:

The key is that Win XP is much too aggressive in "permanently" forcing your
hard disk IDE controller into PIO mode, where the CPU is 100% busy reading
and writing individual bytes of data from the hard disks, rather than
letting the DMA (Direct Memory Access) hardware move the data while the CPU
attends to other tasks.

Apply both sets of registry changes. The first one fixes the current
problem. The second one reduces reoccurance of the problem. Regarding
the step about first applying a hotfix, you can forget it if you do the 
change listed
at the first URL below. You can't download the referenced hotfix anyway... 
:-(

-----------------------------------------------------

solving the dma problem in winxp!!:
http://club.cdfreaks.com/lite/t-60218.html

<excerpt>

you go to the reg. key :
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0001
or 0002 (depending on beeing primary[0001] or secondary[0002] ide channel)

there you modify the DWORD value of :
if the drive is on master: "MasterDeviceTimingModeAllowed" or
if the drive is on slave: "SlaveDeviceTimingModeAllowed"
to ffffffff

then go back to your device manager set your drive in IDE channel properties
first back to pio and then, after confirming, again to dma ...that should do
the trick

</excerpt>

-----------------------------------------------------

IDE ATA and ATAPI disks use PIO mode after multiple time-out or CRC errors
occur:
http://support.microsoft.com/default.aspx?scid=kb%3Ben-us%3B817472

<excerpt>

SYMPTOMS
After you suspending and resume your computer several times, hard disk
performance may be reduced. If you use Device Manager to view the properties
of the IDE channel towhich the drive is connected, the Advanced Settings tab
may show that the current transfer mode for the drive is "PIO Mode."
CAUSE
After the Windows IDE/ATAPI Port driver (Atapi.sys) receives a cumulative
total of six time-out or cyclical redundancy check (CRC) errors, the driver
reduces the communications speed (the transfer mode) from the highest Direct
Memory Access (DMA) mode to lower DMA modes in steps. If the driver
continues to receive time-out or CRC errors, the driver eventually reduces
the transfer mode to the slowest mode (PIO mode).

---<snip>---

In Windows 2000 only, read requests to ATA disks are sometimes issued with a
time-out value of 4 seconds. This occurs when your computer resumes from
standby. This might cause a disk time-out because drives typically take more
than 4 seconds to spin up. This time-out value was changed to 10 seconds.

In Windows XP and Windows Server 2003, this time-out value is always 10
seconds.

An alternate, less-aggressive policy is implemented to reduce the transfer
mode (from faster to slower DMA modes, and then eventually to PIO mode) on
time-out and CRC errors. The existing behavior is that the IDE/ATAPI Port
driver (Atapi.sys) reduces the transfer mode after any 6 cumulative time-out
or CRC errors. When the new policy is implemented by this fix, Atapi.sys
reduces the transfer mode only after 6 consecutive time-out or CRC errors.
This new policy is implemented only if the registry value that is described
later in this article is present.
To implement the alternate behavior (reducing the transfer mode after six
consecutive time-out or CRC errors instead of after six cumulative time-out
or CRC errors), you must modify the registry as described below after you
apply the hotfix.

WARNING: If you use Registry Editor incorrectly, you may cause serious
problems that may require you to reinstall your operating system. Microsoft
cannot guarantee that you can solve problems that result from using Registry
Editor incorrectly. Use Registry Editor at your own risk.

Follow these steps, and then quit Registry Editor: 1.Click Start, click Run,
type regedit, and then click OK.
2.Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0001
3.On the Edit menu, point to New, and then click DWORD Value.
4.Type ResetErrorCountersOnSuccess, and then press ENTER.
5.On the Edit menu, click Modify.
6.Type 1, and then click OK.
Follow these steps, and then quit Registry Editor: 1.Click Start, click Run,
type regedit, and then click OK.
2.Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0002
3.On the Edit menu, point to New, and then click DWORD Value.
4.Type ResetErrorCountersOnSuccess, and then press ENTER.
5.On the Edit menu, click Modify.
6.Type 1, and then click OK.
Note The numbered subkeys that are listed earlier correspond to the primary
and secondary IDE channels on a computer that contains a single IDE
controller. If your computer contains two IDE controllers, the numbered
subkeys for the primary and secondary IDE channels for each of the two
controllers may be:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0002

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0003

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0004

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0005
To verify that you have located the correct subkey, verify that the
DriverDesc value for the subkey contains the string value "Primary IDE
Channel" or the string value "Secondary IDE Channel."

</excerpt> 


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