windows 7 professional

Internal power error sounds like a hardware issue.  I would start by running some hardware diagnostics on the system.  If you don't have any, do a search for "burn-in" or "diagnostics".  You will find several free or low-cost diagnostic tools.  For the most part they all do the same thing.

Dell computers have diagnostic built in.   Turn the computer off and back on and during the DELL logo hit F12.   You should see a option for diagnostic of system utility's.  

Run those,  and give any error the the dell Tech Support when you call for warranty replacement.  Dell's number is (800) 822-8965

I would recommend calling them even if you do show no errors since a fault power supply may not be tested with the diagnostic utility.  Make sure you write down any "stop" error you receive during the blue screen and any other information such as file names.  (.dll or .sys).  You can usually also find this information the event viewer once booted into windows.

If you don't have warranty support post the information found in event viewer here and someone can help you.

BTW if you have formated the drive recently the diagnostic partition may be gone. You can download a .iso and burn it to a cd from the support/drivers page on dell's website.  You just need to enter your service tag(usually on the bottom of the laptop)

Yes, Dell systems have internal diagnostics.  But I do not remember anything in the Dell built-ins that would catch power issues.  Of course, I have not used the Dell diags for a few years so there could be new stuff in there now.

If the Dell diags report not problems, I would still give a third-party diagnostics a try.

New install of Win7 on old computer, or did this come with Win7 already installed?

I just worked on a new Dell that crashes 100% of boot-up attempts when older webcam and USB microphones are attached.

If this is an older computer (XP/Vista timeframe) then unsupported hardware could cause BSOD on boot.