bios not detecting cd dvd and need it to reformat!

Hi

I have a dell inspiron bought with windows 8.1.  i did upgrade to windows 10. I did order the boot disk.  Recently i have tons of malwares, popups and what not.  my computer has started to crawl slower then a turtle.  I  cant know exctly why because drilling my teen is not working, he swears he only went on legit anime sites. yeah right!  

i want to reformat and resinstall factory settings.  but that option in Shift restart mode, is not available anymore.  I wanted  to then resinstall wich i did but realized that there are still many folders that are of softwear i installed in 2014 thereofre, it just reinstalled on top even with the option of a clean install and delete all my files.    so i figured i will reformat via  command prompt and boot via cd, like in the old times.  but bios does not detect cd. i have tried adding it and it was there a bit. then presssing f12 and choosing cd did not boot.   

Then i attempted changing boot mode to legacy secure off...   i see the option of booting cd but it still wont boot.  yet my drive does work in windows.  any ideas at all.    

even with a fresh reinstall the windows is soooo slow. i feel like the sites my dear son went to  are just really really full of viruses or whatever. :( thank you parental control on router netgear that NEVER works.