|It could be anything.|
Can you boot into Safe mode?
Gateway probably came with recovery disks.
How to start Windows XP in Safe mode
To use a Safe Boot option, follow these steps:
1. Restart your computer and start pressing the F8 key on your keyboard. On a computer that is configured for booting to multiple operating systems, you can press the F8 key when the Boot Menu appears.
2. Select an option when the Windows Advanced Options menu appears, and then press ENTER.
3. When the Boot menu appears again, and the words "Safe Mode" appear in blue at the bottom, select the installation that you want to start, and then press ENTER.