Here is what you should try..
1. Go here - Malwarebytes
2. Download and install Malwarebytes Antimalware.
3. Update Malwarebytes. Run a full scan on the C:\ drive.
4. Reboot the PC
5. Before the Windows XP splashscreen comes up during startup, press F8 on the keyboard. Do this between after the BIOS screen and before the XP screen.
6. Choose Safe More with Networking
7. Once in Windows, run another scan with Malwarebytes and Superantispyware. If you couldn't install Malwarebytes before, try to download/install it now.
8. Reboot the PC into regular mode and see if it works.
If not, try this.
9. Click Start>Run
10. Type in 'C:\windows\system32\drivers\etc'
11. On the menu bar, click on Tools>Folder Options.
12. Choose the View tab, and make sure to toggle it to Show Hidden Files and Folders
13. Doubleclick on HOSTS file. Choose to open it in Notepad.
14. Look at the bottom. If it has anything other than this in it, delete it..
Code:
# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost
15. Reboot the PC and try it again.
If those steps don't work...
16. Put your Windows XP CD in.
17. Start your computer and press F12 and/or ESC. This should bring up a boot menu.
18. Choose to boot from CD.
19. Windows Setup will run and load a bunch of files.
20. Once it gets to the Setup screen, press ENTER to setup windows.
21. It should then ask you to agree to the EULA, press F8 to agree.
22. It should then look to see if Windows is installed. If it finds it, it will tell you to press R to repair or ESC to skip past it. Press R. If a screen comes up showing you your disk partitions or asking where to setup Windows, power off the PC.
23. Windows repair should begin replacing the Windows sytem files WITHOUT DELETING YOUR PROGRAMS/DATA. It will then want to reboot.
24. Go through the Windows setup process and put in your CD key and any info it asks for.
25. Once the setup is done, and you are back in Windows, go back to Step 1 and go from there.
If none of these steps work, you are probably looking at re-installing Windows or will need to have a tech take a look at it.