i have a windows xp sp2 system.After i installed avast 4.6,the sytems halts for about 5 mins at startup showing the sand clock even when there is no cpu activity,and then later the pc starts functioning. I can’t understand what’s wrong 
please help!!!
Which firewall do you use?
Can you post a list of the startup applications (links and Windows Registry keys)?
Some applications could help you making this list:
Startup Applications List: http://www.pacs-portal.co.uk/startup_pages/startups_all.zip
Or even:
http://www.r2.com.au/downloads/files/startdelay_v2.1b10.exe
http://www.mlin.net/files/StartupCPL.zip
http://www.mlin.net/files/StartupSelector.zip
http://w1.340.telia.com/~u34011139/bfrmr_creations/warez/Startup-Logger2.zip