As I said, there's no ChromeOS for anything but ChromeBook's. ChromeOS is based on Chromium, and there are several projects made around it to provide ChromeOS-compatible environment for PC.
If your laptop still runs original Windows OS it was delivered with, create recovery media (set of CD/DVD) so you can reinstall it if needed. Most probably, ChromeOS-compatible system will wipe out your hard disk completely (including any recovery partitions).
And talking about performance: Even ChromeOS on a slow PC will be slow. If you weren't able to watch 1080 videos in YouTube under Windows, chances are you won't be able to do that in ChromeOS either.