Hi
For the past week when I start up windows XP, it usually stalls/stops when the 'windows is starting up' screen appears. I have to constantly restart the computer until it eventually gets past the screen. I have noticed if I keep hitting the Enter key, it seems to continue on (I don't know if this is co-incidental or not). Any ideas on what the problem could be and how to fix it?

Does the computer just freeze? Or reboots?

First off run check disk:

start > run > cmd
in the new window type chkdsk/f
when prompted to run on boot choose Y & reboot
this will check for & fix any disk errors.

Also: look in your Event viewer: rt. click My Computer then click Manage then Event Viewer.
Or: Administrative Tools/Event Viewer or Start/Run/ eventvwr
Open the system as well as the application tabs & look for X errors. Click error line for details.
Post back the source & event id especially of errors that seem to coincide with a crash.