So, i installed Avast free a day ago and did a boot time scan. It loads windows then comes up with an avast scan screen in a blue colour then it has loadig dots moving. Then it has the bsod and reboots. Safe mode wont work, nothing will, any help?
Hello piepie and welcome to the forum. 
- What is your OS, 32 or 64-bit?
- What version of Avast did you install? 5.0.677 is the latest version.
- What other security software do you currently have or did you have in the past on this machine including antivirus (AV), firewall (FW), and other security programs? If they were in the past, how did you remove them (the vendor’s uninstaller’s tool or another way)?
- Since Safe Mode will not work, and this is not normal, did it work prior to you installing Avast or is this behavior something new?
- When was the last time you did some kind of malware scan and what kind of scan was it? Did it find any infection?
Can you please check your computer for malware with Malwarebytes’ Anti-Malware (MBAM).
· Download free http://www.malwarebytes.org/ (blue button) for an on-demand scanner.
· Double Click mbam-setup.exe to install the application.
· After install, click update so you have latest database before scanning.
· Under Settings:
o General: Automatically Save File After Scan Completes is checked off
o Scanner Settings: Check all boxes
o Updater: Download and install update if available is checked off
· Once the program has loaded, select “Perform FULL Scan”, then click Scan.
· The scan may take some time to finish, so please be patient.
· When the disinfection scan is complete, a log will appear in Notepad and you may be prompted to Restart. (See Extra Note).
· Click the “remove selected” button to quarantine anything found. You will find the infection details under the Quarantine tab.
· The log is automatically saved by MBAM and can be viewed by clicking the Logs tab in MBAM.
· Copy & Paste the entire report in your next reply.
Thank you.