Have you tried starting in Safe Mode? As the Laptop is coming up, tap on F8 and you should go into the Safe Mode Menu. If you do go in there try the Last Known good Configuation. If that doesn't work, you do need to Format and reload Windows XP. This Laptop is older than 3 years, so you should consider a new HDD then you can move your Data over after you have it running again. Also max out the Memory to 1Gb, which is all you can put in there.