Problem installing anti-virus ?

Hello !
I have just download avira anti-virus for my pc and when I installing it on my computer it takes too much time may be i m attending wrong process to install it. So, plz help me tell how can i install this anti-virus on my pc .

My computer is windows 7 and it has i5 processor with 3 GB of RAM.

Great, most probably your computer is already infected with virus and it is not allowing you to install Antivirus . You may try to go to safe mod, disable all unwanted program and then after that try to install it again.