I got a message on my computer saying that nvata.sys was corrupt or missing. This occurred when I started up a Windows XP machine. I fixed the problem and this is how I fixed it.
But before you try the fix, press F8 when Windows starts up and select the Last Known Good Configuration option. This might fix the bootup problem.
For the fix, you’re going to need another computer with Internet access, a Windows XP installation CD, and a USB drive. Download 7-Zip and install it. Then download nForce4 drivers from NVidia. My machine has a nForce4 chipset. Your machine might have a different chipset. If so, download the drivers for that chipset.
Instead of installing the driver exe, you going to extract nvata.sys from it. Right mouse click on the exe and select 7-Zip->Open Archive. Inside the archive, nvata.sys should be located in \\IDE\WinXP\sata_ide. Copy the file to a USB drive.
Connect the USB drive to your troubled computer and insert the XP installation CD in the CD drive. Reboot the machine. You should see a prompt asking you to press a key to boot Windows from CD. Press a key. Wait for the install CD to run. You should see a prompt of options. Press R for repair. You should be at a console. Select the Windows install that your going to repair. It might be selection number 1. You’ll be prompted for an administrator password. Enter it. You should now be at a prompt much like DOS.
Type ‘map’. Figure out which drive letter your USB drive is mapped to. Once you figure that out. Go into it. Locate nvata.sys in your USB drive. Now copy the nvata.sys file from you USB drive to your machine, e.g. ‘copy d:\nvata.sys c:\windows\system32\drivers’.
Remove your USB drive and Windows CD. Reboot your machine. And your problem should be fixed.