Computer runs slow after installing Avira Anti Virus

I have HP laptop. The machine specification is core i5, DM4 Pavilion 2.27, 1 GB Video, 4 GB ram and 500 GB hard disk. It has Genuine Windows 7 home premium (64 bit). I installed Avira antivirus program through the internet free. The problem is that the machine is responding very slowly and some of the applications are not executing properly.
I tried to open Corel Draw application, which first opens properly, and then hang for few seconds and stop the program. I cannot understand why this issue is happening in Laptop? Is this for the Avira application or for another application, is there anyone having similar information on this problem? Please help me to solve this.
