comp starts as far as user log in then takes over 5 mins to log user in

Did this just start to happen out of the blue, or was any software, or AV/software updates installed just prior to this occurance?

Please provide a bit more information as to;

1. XP Service Pack - 2 or 3
2. Anti-Virus package being run
3. Firewall being run
4. Any other spyware/malware programs being run
5. Programs being run on startup (Start, (All) Programs, Startup)

Happened over 6 month period getting much slower. No new programs added, using xp service pack 2
Norton A.V. Windows firewall Deleted programs running at start up that i regonised did not need.
Up dates downloaded from Windows Update nothing else.
Thanks for help