Welcome to Windrivers rikandsheila

Alot of these older laptops have the bios on a partition on the hard drive instead of a chip. When you upgrade the ram, this partition has to be rewritten and possibly increased - yes this does mean having to completely reinstall everything!

Panasonic have some great support, but unless you register (free) you cannot access the downloads or the faqs.
here is the toughbook support

Sign up and get the user manuals and search the faqs for upgrading ram. You will also find bios and driver updates there.