Windows Vista Desktop won't show up!

I was using Home Premium happily until one day I downloaded two key values from www.howtogeek.com about slow motion for the window showing up.
The problem is: every time when I boots my computer, everything works properly until the final step, showing up the desktop. I can only see my mouse and that's all. Now I can only use the computer if I start the task manager and start the explorer.exe. I deleted that 2 EXTRA key values that I downloaded, I also scanned my computer with Windows defender, Trend Micro PC-cillin Internet security, Spybot-Search&Destroy and Adware Personal. The problem still didn't go away, what happened???