I am running avast! on my main PC and doing some testing with AVG on my laptop(Yikes) to figure out a email scanning question when using YPops. I removed Norton thouroughly before installing AVG. First when it installed the SMTP was disabled like this, SMTP*: and sometimes when the system boots it gets to the XP logo and then a black screen appears. This is random(It could be another problem). I know alanrf used to do some testing with that product so if possible I would like some input. The folks at the AVG forum seem to blame everything on Norton. I have removed Norton before in fact the system I’m using to write this had Norton on it and now avast with no problems. I plan to switch the laptop over to avast! soon as I’m done testing AVG because it seems a bit buggy and fussy. Thanks for any input!! ???
Norton is nororiously difficult to remove and remnants may cause problems, when you say you thoroughly removed Norton, did you take the steps in these links (which ever is relevant).
The NAV2003 removal tool can be downloaded here: ftp://ftp.symantec.com/misc/consumer/Rnav2003.exe
Although this has nothing to do with avast and should be on either the General or off-topic forum.
The AVG mail scanner in the presence of any other antivirus (Norton, avast, etc.) is very unstable.
I won’t be surprised that everyone blame everything on Norton ;D
Try removing Norton, then AVG, then clean registry and files left behind by both, then install avast and be happy!
Yes Technical: it’s strange but maaaaaaany persons continue to keep 2 antivirus programs running in the machine at the same time. 
Thanks for the input everyone, Next time I’ll post in the proper spot, sorry!! I’ll do another cleanup and VERY HAPPILY install avast! I am really impressed with avast! so far. I’m sure glad I found out about it and installed it!! ;D