Lightroom CC unable to start

I just ordered the CC for photographers, downloaded and installed Photoshop and Lightroom.

Photoshop started up okay, although it seems to run very slowly compared to CS6 version. Light room however won't start up at all. Each time I try, I get this message:

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lightroom.exe - Application Error

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The application was unable to start correctly (0xc000007b). Click OK to close the application.

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OK  

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I closed everything down and rebooted the system twice, but it makes no difference. My computer is:

1. Dell XPS desktop i7 processor
2. 12 GB RAM
3. 1 TB hard drive plus second drive for photos, plus external "my book" back up drive
4. Windows 7 OS 64-bit completely up-to-date.

Any ideas what to do next? I can't work without Lightroom.

thanks,

Ed