I have to ask -
1. Are you on a domain, workgroup, or just a home LAN?
2. Did this problem begin occuring after installing something that runs as a service?
3. Do you do ANYthing with MySQL Server?
4. Run Reg Cleaner from AATools -
Statistically I can say this, it could potentially be a 50/50 Hardware/ Software problem. Start by stopping all non-windows-essential services, and see if there is still a hang -
Control Panel --> Administrative Tools --> Services,
disable non-essential software -
Start --> Run --> msconfig --> Startup.
Give this a try and let me know if anything changes.
A few other times that a similar situation has happened in my office, I have used combofix from Bleeping Computer -
it's an extremely powerful malware cleaner, and if none of the other responses work, give this a shot, you may find that you have an extreme case of malware infestation.
Beware of hackers bearing executables. Happy Hunting. 'irc.2600.net'