External DVD/CD Drive won't Work

Hello,
I have a Toshiba Satellite A60 laptop. A while back the internal DVD/CD stopped working and the drive disappeared
alltogether.I went on the internet and tried a number of suggestions without success. I then purchased and reinstalled a new drive without success. I have now purchased a new external USB2 DVD/CD drive which is supposed to run independently using WinXP O/S. It doesn't show up as a new drive either!!
If Windows is the problem I need a CD to work before I can format C and reload WinXP. What is the problem?
What can I do about it?

Thanks for your help,

Catch 22