|"So why not use my old one."|
You don't mention make/model of the laptop you're trying to "downgrade". Before you attempt any downgrade, you need to verify that there's available drivers for the machine so all hardware will work properly.
"Reading some forum post about using nlite to slimline drivers but I have not had any luck."
nLite isn't necessarily designed to slimline drivers---though it can be used to integrate drivers and service packs. It's main purpose is to re-create an installation disc to reduce the size of the installation of Windows itself (thus making it generally faster). A good review and guide can be found here (the guide uses an eeePC, but it can be used for any machine with some modifcation):
"Channeling the spirit of jboy..."