thanks for the reply
I have visited the atmel site and searched for avr studio
I find many software on that page
it contains many Softwares like AVR Studio 4.17 (build 666), AVR Studio 4.16 SP1 (build 638), AVR Studio 4.16 (build 628)
and many more
Which one should I download?
and is it a free version ? I mean full version
or is it a demo/ trial version ?
Yes, it's free, and the full version. I don't think I have the newest version, if it works, why upgrade... Would go with the most recent, for a new install. It's pretty easy to use, and a lot you can do with it, pretty much everything you need to use their chips. There is also a free 'C' compiler, but I don't program in 'C', but did use it once to build a Hex file, from an internet project. Been using BASCOM Basic, which is also free, and fully functional, but limited to 4k of code (plenty), cheap to purchase if you need more.
AVR Freaks is a good place to get AVR questions answered, plenty of good resources there. Probably a good place to check on different AVR Studio versions. I've only installed two, no problems either time, been a couple of years...