The following may be a possible solution for those users who cannot get XP to start or cannot login or get a BSOD after login.
You will need the following:
1. Access to another computer ( any Windows computer will do that has a USB port )
2. SATA/IDE to USB patch cable ( these are not expensive and all computer shops keep them )
The procedure is as follows
Before you start disconnect the computer with the Avast problem from the Internet.
1. Switch OFF the computer with the Avast problem and remove the mains cable from the wall
2. Remove the System Disk from this computer. I will call this disk DISK_AP (Avast Problem)
3. Start the other computer
4. When the other computer has started use the patch cable to plug into a USB Port DISK_AP
5. Using Windows Explorer go to DISK_AP
6. Go to the folder Programs on DISK_AP
7. Scroll down until you find the two folders Avast and Avast Software
8. Change the names of these folders to STOP_Avast and STOP_Avast Software
9. Go to the Windows folder on DISK_AP
10. Scroll down to the folder system32
11. In the system32 folder on DISK_AP click on drivers
12. Scroll down the list until you come to a set of drivers that all start with asw
13. Change the extension of each of these files from .sys to .bak
14. Click on the USB icon in the System Tray and click on the DISK_AP to safely remove it
15. When Windows tells you that it is safe to remove, then remove DISK_AP from the USB port
16. Reinstall DISK_AP into its computer
18. The computer will now start without any problems
Once the computer has started you can then decide what you want to do next........ for example....
a) Uninstall Avast 9.xxx and reinstall Avast 8.xxx
b) Uninstall Avast and install a different AV product
Whatever you decide to do you will need to clean up the Registry when you are finished. One of the best and safest Registry cleaners is Advanced Uninstaller Pro 11 which is available at this link:-http://www.advanceduninstaller.com/
REMEMBER !!! Always create a Restore Point with System Restore BEFORE doing anything to the Registry !!!