HP Pavilion DV2000. Just replaced the mains transformer as this did not appear to work. Laptop

Question

Just replaced the mains transformer as this did not appear to work. Laptop did not light up. Received new one today. Laptop now comes on but will not start up.

First page shown reads "we apologise for the inconvenience but windows did not start successfully, A recent hardware or software change might have caused this etc etc.
Page then goes to the blue Microsoft XP page and looks like something is happening with the timer thing going across the page but it then reverts back to the initial page as above. Can you help. Know nothing about PCs when problems arise!