I'd copy whatever data you want to keep & restore to factory
settings. If you can't restore to factory settings, you'll need to reinstall everything from scratch including all your drivers. Look at Device Manager & make a list, then download them from your manufacturer's web site. After reinstalling, you'll need to install all your applications. That includes download Windows Live Essentials from the MS web site and setting up WLM with your accounts. As Jimmy Greystone points out, those registry cleaners are snake oil, do no noticable good, and can create problems.
When you've gotten your system back like you want it, I urge you to get yourself an external hard drive and a good 3rd party backup program. You can set it up to do everything automagically at the time and frequency of your choice. 1 TB external hard drives are about $70 these days and a really good FREE backup program is the Easeus todo backup free which you can download from
http://www.todo-backup.com/products/home/free-backup-software.htm . That can save you a lot of time and frustration the next time something like this happens. Sooner or later it happens to all computers for one reason or another.