Click Start, type regedit in the Start Search box, and then press ENTER.
If you receive the User Account Control dialog box, click Continue.
Locate and then click one of the following registry subkeys:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\IastorV
In the right pane, right-click Start in the Name column, and then click Modify.
In the Value data box, type 0, and then click OK.
On the File menu, click Exit to close Registry Editor.
This might work! There's something that looks like this in XP, I just don't remember. If both Msahic & IastorV both exist they both need to be modified ( at least 1 of them should be there ). What I do remember, there was a downloadable registry fix for this issue..... could have been 5 years ago