Please run the diagnostics to check the hardware functionality. Here are the steps:
You may refer to the link http://dell.to/1bV0cp4 for steps on how to navigate to safe mode in windows vista.
Once you are logged on to safe mode, log on to the administrator account. Please perform the steps given on this link http://dell.to/1eIaCdi.
Hope this helps!
Keep me posted with the results. I’ll be glad to assist.