computer is making noise like a spinning cd when no cd is inserted

Hi,
 
1. Did you make any changes on the computer recently?
2. Do you've any security software installed on the computer?
3. When you hear noise, does the CD/DVD light blink on tower i.e. CPU?
 
If there is no disc in the CD/DVD drive and if this issue occurs, that means some program/programs is/are trying to use a lot of system resources. There is a possibility of virus running on the computer and also due to errors on the hard disk.
 
It's recommended to first run virus scan on the computer and check if the issue persists. To run full service scan, visit the following link: http://onecare.live.com/site/en-us/default.htm

If the issue persists, run check disk on the hard drive. To do this, follow these steps.
1. Click Start, type cmd, right click on cmd and click run as administrator.
2. Type chkdsk /f /r and hit enter.

For more information on check disk, check this link: http://windows.microsoft.com/en-us/windows-vista/Check-your-hard-disk-for-errors
 
If the issue still persists, then follow all the steps mentioned in this article to find out the culprit that's causing this issue: http://support.microsoft.com/kb/929135
 
NOTE: Don't forget to follow step 7 to reset the computer to start as usual.
 
To troubleshoot on system performance, check these links for more information.
http://www.microsoft.com/atwork/maintenance/speed.aspx
http://support.microsoft.com/kb/959062
 
Hope this helps.
 
Regards,
Syed
Microsoft answers support engineer.