To be more productive with my responses.
DMA step down caused by SF I/O authorisation errors on the IDE channels, (WIn 2000 to XP steps down DMA access speed each time this occurs, eventualy that will drop into PIO mode, rendering playing of DVD video almost impossible and attempts to Burn CD/DVD's with just create coasters, thats assuming you can put up with the 1 to 2 hour burn times in that mode).
Warning not all current CD/DVD drives support PIO mode for any extended period of time. They can interpret this mode as an overburned disk and slam the laser mount into the case, stripping the worm gear and trashing the drive. The only cure for that is to replace the drive.
DMA Step down: (How to fix this)
1. Use the SF removal tool.
Click Here to get it.
2. Go to the device manager and (left click) on DVD/CD rom drives,
3. (Right click) on each drive and click uninstall. (cancel the message to reboot)
4. (Left click) IDE ATA/ATAPI controllers.
5. (Right click) the primary IDE channels and (left click) uninstall.
Do the same for the secondary IDE channel (and the IDE controller if its really stubborn).
If no hardware failure has occurred when you reboot, The system will search and reload the drivers, (Reinstating DMA instead of PIO mode access).
(Code 41) in the device manager.
(Code 41) means: "Windows successfully loaded the device driver for this hardware but cannot find the hardware device". In al sense and purposes it looks like Hardware failure.
To workaround this behavior:
Create a restore point start menu-all programs-accessories-system tools-System restore and follw the prompts.
1. Save the filter driver registry entries, just in case of problems, goto start menu-run type in "CMD.exe" without the " " then (left click ok) and at the Command shell prompt type in:
regedit /a SaveFilters.reg HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Class\{4D36E965-E325-11CE-BFC1-08002BE10318}
and 'hit' enter, that should save the filters section of the registry.
2. using 'notepad' Copy / Paste the following and save it to a NoFilter.reg file in the root , windows or ,my documents folder:
REGEDIT4
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Class\{4D36E965-E325-11CE-BFC1-08002BE10318}]
"UpperFilters"=-
"LowerFilters"=-
3. Merge the NoFilter.reg file with your registry or start menu-run type in "regedit /s NoFilter.reg" without the " " and click OK.
4. Shutdown and restart your computer.
If you notice loss of functionality in any remaining DVD/CD-ROM software, you may need to uninstall and re-install it.
Oddly enough you may also need to uninstall and reinstall windows media player.
Should it all go belly up, boot into safe mode and carry out a system restore to the previously saved restore point, or at a command shell type "regedit /s SaveFilters.reg" to merge the previous filters back.