is it dangerous

i got a new cpu assembled about 15 days ago
intel core i5 2320 3.00 ghz
8 gb of ram
saphire amd radeon hd 5450 2 gb ddr3 graphics card

yesterday after i shut down the computer i got a dark blue screen which dissapeared suddenly
the first or second line read that windows has detected a serious issue.
then my pc restarted and black screen came reading that windows did not shut down succesfully
then i chose start windows normally
then i shut down and there was no issue and still there are no issues this post was also written from this copmputer.is there really any serious problem.

Go to Start -> Search -> c:\windows\minidump to see if your computer has blue screen'd and automatically restarted. Typically, your settings should allow a crash to output what is called a dump file. This is a memory dump created by Windows as it detects that it is no longer capable of functioning, usually due to a hardware, serious software conflict, or memory error.

If this area is blank, and the issue never pops up again, considering letting a few days ago by. If this is a new set up, you are still under warranty. You may want to test the integrity of your hardware using what are known as burn-in utilities. Many of these utilities are free, used in IT pro environments extensively, and will help determine if your CPU/GPU/RAM and hard drive components can handle stress.

Some great samples of this freeware:

prime95 (burn-in CPU and memory stressing)
memtest86+ (CD/DVD/USB for booting into a thorough RAM scanning test)

For graphics cards, many benchmarking tools are out there for commercial use, which are also used for stress testing. One of the best ways to really test your graphics card to the limit, is to, literally, run a program or more likely, play a highly intensive game for a prolonged period of time. This is the cheapest way. If your system suddenly crashes and you get a blue screen listing suspect files from AMD or NVIDIA, you will have a good idea something is wrong, especially if it happens consistently.

Unfortunately, you're going to see what I'm talking about with PassMark right here: PassMark BurnInTest software - PC Reliability and Load Testing

It costs money. We have no affiliation or coupons to give you for this one. If you want to try something different, run your GPU with a high powered game. If the system consistently freezes, we can even analyze minidumps for you. But its probably the root cause.

If your system goes dead for no reason at all on the desktop with nothing running, it could be any manner of issue, and that is why you should run prime95, memtest, etc.

Before doing this all, go to Start -> Run -> Event Viewer
Start -> Run -> View reliability

Look at these areas to see what could be wrong. There is no silver bullet for these problems until you, yourself, collect additional information. If the build is not working for you, it could be any number of issues, but if you get to the point that you've been driven mad by the errors, be aware of warranty and RMA time. If you find a faulty component, you may need to work fast to have it replaced.

the minidump folder is empty,i have done 2 shutdown and 2 times started my computer there are no issues. is everything ok thanks for that

I would say right now no, there is nothing to worry about. If it was an isolated incident, then it could be useless to get all worked up over it. I would watch it the next few times you shutdown or reboot. Now that is not to say to reboot five times in a row, just use the comptuer and when you do shutdown or reboot, keep an eye on it. If it dose it again, reseeting the graphics card and or RAM could and or any other cards you have in the system could help. Though like usual the sugestions that Mike gave a great to go with.

I still get something like that once in a while.
Most of the time it's just some glitch in the process.

Occasionally my computer fails to boot, but when restarted it always goes OK.
I don't even get the Widows didn't start message.

If it happens more then once then I start checking.