I've gone through this a few times. Once in awhile, manually resetting it as per the instructions DaChew showed you, didn't stick for me. So, I came across these hints.
MY REGISTRY HACK:
First go into Tools, Folder Options, View and uncheck Hide extensions for known file types. Click Apply.
Then open Notepad and copy/paste this: (without the -------- parts)
Windows Registry Editor Version 5.00
Give it a name like Reset DMA and save it on your desktop or wherever. (I keep mine handy in my Tools folder for whenever I might need it again.) You'll get a warning when you save it. Ignore that and say yes. If you've done it right, your saved file should now have the registry icon instead of the notepad icon. Just click it to merge it into your registry and reboot.
Go back into Device Manager to confirm the change from PIO to DMA.
(Then don't forget to go back into Tools-Folder Options-View and re-check the Hide Extensions of known file types after you are finished.
This is another registry tip I found, but I have not used this one. (It looks like this is a way to manually delete the values that are reset when using the registry hack that I use.)
1. Open RegEdit
2. Find the following KEY:
3. The last four digits will be 0000, 0001, 0002, 0003, and so on.
4. Under each key, delete all occurences of the following values:
5. Reboot the computer. Windows will now redetect DMA settings.
As always, before doing anything like this, make a System Restore Point or registry backup first, as a precaution.
Edited by mommabear, 14 December 2007 - 07:54 PM.