Hi,
I have a dvd-rom that was working fine but suddenly one day its not there anymore when I open My Computer. Same thing in Device Manager, as if it's not connected at all.

I tired unplugging and plugging the IDE cables but still nothing happens.

Attached are the errors shown in the Event Viewer

MoBo: ASUS P5ND2 SLI

The nvatabus issue appears to be an issue with the NVIDIA chipset drivers.

It results in many different behaviors as seen here:

NVIDIA Forums > nvatabus

I would go to the ASUS driver page and load the latest drives and check for any possible BIOS updates.

You could also try clearing your CMOS.

sorry for the late reply,
I already have the latest drivers and BIOS.

How can i clear the CMOS?

thanks..
By the way after reading all the post in the link you gave me i noticed they have a different problem than mine.

Their Event Viewer shows the following:
Source: nvatabus
Event ID: 4
Description: Device slot returned an invalid status value. See data for detailed information.

While mine shows:
Source: Service Control Manager
Event ID: 7026
Description: The following boot-start or system-start driver(s) failed to load: nvatabus.

Totally different!!!

So are you saying clearing the CMOS did not help any?

Try This
This method provides step-by-step instructions for how to use Registry Editor to delete the following corrupted Registry entries:UpperFilters
LowerFilters
UpperFilters
LowerFilters
Step 1: Start Registry Editor
Start Registry Editor.
Step 2: Delete the UpperFilters registry entry
In Registry Editor, expand My Computer, and then expand HKEY_LOCAL_MACHINE.
Expand SYSTEM, and then expand CurrentControlSet.
Expand Control, and then expand Class.
Under Class, click {4D36E965-E325-11CE-BFC1-08002BE10318}.
In the details pane of Registry Editor, on the right side, click UpperFilters.

Note You may also see an UpperFilters.Bak registry entry. You do not have to remove that entry. Click UpperFilters only.If you see the UpperFilters registry entry in the details pane of Registry Editor, go to step 6.
If you do not see the UpperFilters registry entry, you still might have to remove the LowerFilters registry entry. To do this, go to "Step 3: Delete the LowerFilters registry entry."
If you see the UpperFilters registry entry in the details pane of Registry Editor, go to step 6.
If you do not see the UpperFilters registry entry, you still might have to remove the LowerFilters registry entry. To do this, go to "Step 3: Delete the LowerFilters registry entry."
On the Edit menu, click Delete.
Click Yes when you receive the following message:
Are you sure you want to delete this value?
The UpperFilters registry entry is removed.
Step 3: Delete the LowerFilters registry entry
In the details pane of Registry Editor, on the right side, click LowerFilters.

Note You might see a LowerFilters.Bak registry entry. You do not have to remove that entry. Click LowerFilters only.

If you do not see the LowerFilters registry entry, unfortunately this content is unable to help you any more. Go to the "Next Steps" section for information about how you can find more solutions or more help on the Microsoft Web site.
On the Edit menu, click Delete.
Click Yes when you receive the following message:
Are you sure you want to delete this value?
The LowerFilters registry entry is removed.
Exit Registry Editor.
Step 4: Restart your computer
Restart your computer. After you have done this, try to access the CD or DVD drive. If you can access the CD or DVD drive, and if you do not receive an error message, the problem is resolved. You can reinstall your CD or DVD writing or recording software.

Although the above is a work-around for a drive detected but not working properly the problem here is that the BIOS does not even see the drive.

The question still remains: did you clear your CMOS?

perhaps it's the cables or the jumper on the drives?

First try to check power Plug that is properly connected to the DVD Rom or not.