The PSUs that come with cases are often a bit hit and miss on quality, yours will run your pc certainly long enough for you to decide if you want to keep it or not.
I've had some that have sounded like a tornado with flaky voltages, others have been as good as any 40 quid supply you can buy.
Most have had cheesy names like "WinPower" lol
You may even be better off with that supply as a lot of people seem to be having problems with their expensive supplies at the moment (not quality but more incompatability)
As SPW has already said, welcome to the forum.