Hi Max ( again ! ),
Try this first - the "simple" solution ...
Power on the PC and keep hitting the "F8" key until the PC has passed it's power on self test when it should open up a menu with an option to select "Boot Using Last Known Good Configuration".
If you get this, select the option and the PC should boot up using the last known good configuration.
This doesn't always work though - it depends on what has gone wrong in the first place, so if not you'll have to move on to the less simple method as recommended by Microsoft here :
Recovery from corrupted registry...
Good luck - if you the first solution doesn't work I think you'll need it - I'd say if you need to use the XP CD that you have then try it - it will either work or it won't !
