Windows XP was taking forever to load up, and by inspecting the windows task manager we realised the "System" process was taking all of the CPU. Below are solutions that have worked for us.
Boot windows into safe mode
Set unnecessary services to Manual. This will prevent them from starting up in normal mode.
Reboot and start as normal.
In our case, we disabled Trend Micro's PCCillin and some Cisco VPN software. This allowed windows to start up normally.