Windows 7 - IRQL not less or equal blue screen error

I was trying to install Avast Internet Security version 6.0.1000 when a blue screen with message IRQL not less or equal was shown and my Laptop had to be shut down failing to install the software. I had experienced same message when I tried to install Norton 360 and Norton Antivirus 2011 and also Kaspersky Internet Security 2011. However, in later cases i was able to install the software but when I had to reboot my Laptop for completion of installation it showed the blue screen with IRQL not less or equal and I had to use system restore to make my laptop work normally. I have up-to-date Windows 7 Ultimate SP1 and update my windows frequently. I own a Dell Vostro 1014. Please help. However, when I installed Avast Antivirus 6.0.1000, it worked,