for the bios, find the product key, go to the web site, type it in. select your computer, go to the download section, you'll find all of your sofware for that computer, but make sure this (IS) your computer. it might have a few different bios downloads, just look for the youngest one. NO product key? search for the computer manually.
for the freezing. sacan for viruses, avg free is the best. also windows defender, and also windows update. ccleaner for unused files and broken file paths, and defrag.
aslo what nanobyte said about the heat sink.
if any of this doesn't work. do a system restore, this will not affect any of your personal files of any kind. you might have to reinstall some programs, but that depends on how far back you restore your computer and when the programs were installed.
hope you get some where. best of luck.