Hello swifty and welcome to Seven Forums.
Just for confirmation, you were able to do a successful system restore to 12/22. However, you are still unable to play a video from the hard drive using WMP or VLC. And you still can't watch You Tube videos while using Firefox. When you uninstalled/reinstalled your display driver, did you get the latest driver directly fom Dell? Did you make use of their diagnostics?
Support for Home Users | Dell US
You might want to go through these tutorials prepared by one of the Forum experts. They have some additional suggestions on things to try. It's possible your computer is having some hardware issues and the first tutorial addresses some of the common diagnostic tools you can use.
Troubleshooting Steps for Windows 7
Troubleshooting Windows 7 Failure to Boot