DVD Drive missing fom 'My Computer'

Hi, I am using Dimension 4600 with CD DVD combo since two years and never got this problem before.

After installing itunes software for ipod, suddenly dvd drive is missing from 'my computer'

It is no longer showing me D: letter assigned to dvd drive.

 

In device manager it shows me yellow Exclamation symbol besides dvd drive. Property says

 

Windows successfully loaded the device driver for this hardware but cannot find the hardware device. (Code 41)

Click Troubleshoot to start the troubleshooter for this device.

 

However, I beleive that it is not a problem with connection to physical device, but more because of driver etc, as I haven't touch CPU at all.

 

Driver installed is HL-DT-ST RW/DVD GCC-4481B

 

Can anyone advise me what is the reason for this problem and how to solve it?

 

Many Thanks