arduino uno connection problem

I recently got my arduino uno but not able to upload any program on it. I searched on internet a lot but found nothing useful.
I am using win 7 64 bit and using atmel studio 6 to program arduino uno. By following the different tutorial available on internet to program uno using atmel studio 6, I compiled and tried blinking led code. It compiled successfully but on uploading it to uno, I got error message "avrdude.exe: ser_open(): can’t set com state for “\.\COM7"”.
COM 7 is the port for my uno board.

Prior to atmel studio 6, I tried the led blinking program using arduino IDE, I could upload the program on uno but after that whenever I try to upload the program, it always say that the port is currently busy. I dont know how to free that port.

Please help me, I am new to arduino and just beginning with it and find myself stucked at the very starting phase.

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