Help Adding/removing operating systems

I am having multiple problems with a laptop that runs 2000. The person who used the PC before I got my hands on it had some virus/spyware issues and now many differant functions do not work. Long story short I need to wipe the hard drive of 2000 and install 95 with an upgrade to 98. I have CDs and the keys but don't really know how to go about reaching cleaning/installation process. Could someone please walk me through the process?