I just installed Avast, but after I installed it any attempt to connect to the internet crashes my computer. System restore or uninstalling Avast fixes this problem. However, I really want to install Avast. Can someone help me please?
What AV did you have prior and how did you remove? Did you run the vendors removal tool to eliminate remnants ?
Many aV removal tools can be found here http://singularlabs.com/uninstallers/security-software/
Some more information about what version of avast your installing and your system information would be helpful also.
What avast version are you using, free/pro/ais ?
What is your operating system and firewall ?
What other security applications do you have installed ?
I disn’t have any AV, it’s a brand new computer. I’m using avast free edition, and windows 7 home premium 64-bit. Please let me know if you need other info.
Most new computers come with a pre-installed AV, you would need to remove it then run the neccesary removal tool to clean up leftovers.
Ok, in tyhe programs list I seem to have Norton 360 installed. Where can i find a removal tool for that?
In my first reply to you, uninstall norton first from programs and features then reboot and run the tool ( download the tool and save first befor deleting norton ), you also might have to reinstall avast as it may have been corrupted by norton being installed.
Thank you so much, it worked! I have never been so relieved, thanks for taking the time to help me out.
Your welcome 
You can also run a manual search through your system for Norton and Symantec and delet anything found under those names.