It is usually all the garbage that slows down your pc. I know when I perform some maintenance on my computer, it runs a bit more smooth. At one point I had about 5 GBs left on my hard drive, and once I cleared up a lot of space, my computer started to run again.

It is easier if you just sync all of your bookmarks and what not to your chrome account. That way if you can keep all of you bookmarks if this situation ever occurs again. As for the games, I assume you had them on steam so the only problem would be downloading them again.

You should invest in an external hard drive. You can keep all of you excess files and games on it to save space on the computer.