First off I am a bit confused.
Was the old problem solved?
If this is now a new problem I will probably just move it to the XP section.
I will look up that Dell model but just for now I will say you should use the Dell recovery CD or partition.
Drivers & Downloads
Dell Solution Network: Knowledge Base Article
Restoring Your Computer´s Software to the Factory Settings
Dell - Support
If you are saying for example there is Vista on this laptop and you want to overwrite that OS then that is a different question altogether.