If I can just get this problem solved I can first uninstall Norton and then reinstall your software. I do not want to reinstall XP if at all possible.
OK, you're saying that it doesn't work to press F8 just before the first Windows XP progress bar (on black screen) appears and run the safe mode?

If you can get access to the disk (e.g. via the Recovery Console, or using a boot diskette, if your system disk is formatted as FAT/FAT32), all you need to do is to delete the files aswmon2.sys and aavmker4.sys in the \windows\system32\drivers directory (the avast device drivers)...
Yes I DID say what operating system I am using.

sorry for that, I kinda overlooked it...
One more thing: while installing avast!, didn't you get a warning message saying that Norton is installed and that is it discouraged to run these 2 programs together?
Thanks,
Vlk