I'm moving this to the General Tech forum, as it's not a Windows specific error.
You'll have to be much, much, much more detailed with your postings in order for people to help you with problems like this.
It sounds like the motherboard installation went quite smoothly for you. If you look in whatever documentation Dell included with your PC and/or motherboard you can find out what this error means. It may also just plainly state it on the screen as it says 'hit f1 to continue'.
Again, we need much, much more detail in order to get into a more detailed analysis. Listing your complete and detailed PC specifications, and perhaps taking some photographs of your monitor as these errors messages show up on screen would be very helpful. 
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