To uninstall avast i downloaded a file named aswclear.exe and i need to start up my computer on safe mode. How I do? I can only go in Setup BIOS and Boot service. Do I need the windows XP cd ? how do i Boot on safe mode? Thank you.
To uninstall avast all you need to do is use Windows add remove programs as for normal program uninstall. You only need the uninstall tool if you can’t use the windows add remove programs. So are you experiencing a problem with add remove programs ?
Running in safe mode avast doesn’t run so the avast! self-defence module won’t block it, see image.
Booting into safe mode http://www.pchell.com/support/safemode.shtml
Why do you want (need) to uninstall avast? 
I uninstalled it and later, i restaurated my computer to a date before… Now it doesnt want to get out and everytime i start up my computer: it sends me an error message.
And i dont have the first page where we can see the memory and all of the stuff at the beginning of the starting up process. So i cant use F8… How can i get this page?
If you restored your computer to a previous state, you need to boot in Safe Mode and run the uninstaller from there.
Or restore your computer back to the original situation and then repair your avast installation, boot, uninstall through Control Panel.