Well, I'm no expert, but my guess would be that your Windows Explorer file has been ruined. It's the file that includes the taskbar. Try to find the file explorer.exe for your Windows version online, and then replace it with the one on your PC. I don't know about 64 bit version, but for normal Windows, put it in:
C:\Windows\explorer.exe
But don't take my word for it, I don't know for sure.
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