Crash While Installing

After numerous problems with AVG i was recommended Avast to use. After downloading the install file, i proceeded to install Avast Free. I walked away for a minute and when i cam back my computer was restarting. Once it started up Avast started but there was numerous issues and services not running, not even the real-time protection. Also it wasn’t in the Control Panel - Add/Remove Programs. So i got the removal tool from the site and removed it. Re-installed and watch the process. Once it installs it runs a quick scan and that when it crashes and reboots. Is there any known solution to this problem?

did you uninstall AVG before installing avast?
have you run AVG removal tool to clear any leftover files that may conflict?
do you have any other security programs installed?

I have AVG completely removed. Also i have Ad-Aware installed, but how does that affect the fact that when its done installing it starts to run a scan and then restarts my whole system? Once it reboots it shows that my trial is up and its out of date and everything its like it doesn’t install the whole program