No - it will not hurt it to turn it on without the aux power connected -- it just will not run stable in 3d mode but the PCI-e connection to the MOBO provides enough power to run the card in 2d mode usually - so depending on the card it might boot OK without it connected but crash when it doesn't have enough power to run full on - or it will make a annoying sound to let you know you forgot to connect it ! (some manufacturers have them set to make an alarm sound if the power connector is not plugged in!)
Just shut down the system plug it in properly and then turn it back on and you should be fine.
Thank you JDFan, very happy to hear you say that...
Wouldnt mind but im currently studying computers... good thing the course is mainly focussed on programming
Thanks again bud
No problem -- That happens a lot so the manufacturers have made sure they will not be damaged if it is forgotten or comes loose for some reason and most cards will emit a high pitch beeping to warn you if it comes loose - figure the PCI-e slot will provide up to 75W which is enough to run a 5770 in idle and 2d mode but not enough for full load where the card can use about 110W so if you do not have it plugged in the system will fail under load since it can not get enough power to keep the card running (this in itself will not damage the hardware but can be a problem if the shut down occurs while the HDD is writing to itself from cache or similar since the data might be corrupted (just like anytime you unplug the system) so not something you would want to do for an extended period !