Problems in the operating system

Possible errors to the Windows XP Pro SP3:
 

When you boot with Windows XP Pro with SP3 it ever gets to the login window for user authentication, never moving from the Windows logo without giving any error message.
 

Sd problem solution:
 

Keep pressing the F8 key while turning on the PC. This should show you soon
a Windows Startup Menu. And then choose to start in Safe Mode and
precione the ENTER key. Notice all the Startup in Safe Mode, if you can
make all the Windows Startup, I mean that is on track. After that, go to my
Computer, click the right mouse button on the C: drive, click
Properties, choose the Tools tab, click Check Volume, and follow
instructions.
 

 Soon then restart your PC normally and make the verification of Volume C: is the Hard Disk
performed. Wait a few minutes or even a few hours because it will depend on the capacity of your hard drive. After that let Windows restart normally. If this does not solve the problem, run the Antivirus in Safe Mode (if you can start in Safe Mode), insert the Windows XP CD in the CD / DVD, and reboot the PC. Choose the option to Repair Windows XP. Look for any documentation
Your Windows XP and CDs

Another solution is to format your PC and install the operating system from scratch.