Correcting Windows Host files if a trojan alters IE settings
Symantec provides good instructions on how to correct issues associated with the Windows host files if a virus or trojan horse modifies it in blocking or redirecting IE to certain sites.
http://www.symantec.com/avcenter/venc/data/trojan.ecure.html
How to repair the Windows Hosts file
Note: The location of the Hosts file may vary and some computers may not have this file. For example, if the file exists in Windows 98, it will usually be in C:\Windows; and it is located in the C:\WINNT\system32\drivers\etc folder in Windows 2000. There may also be multiple copies of this file in different locations.
Follow the instructions for your operating system:
Windows 95/98/Me/NT/2000
1. Click Start, point to Find or Search, and then click Files or Folders.
2. Make sure that "Look in" is set to (C:) and that "Include subfolders" is checked.
3. In the "Named" or "Search for..." box, type: hosts
4. Click Find Now or Search Now.
5. For each Hosts file that you find, right-click the file, and then click Open With.
6. Deselect the "Always use this program to open this program" check box.
7. Scroll through the list of programs and double-click Notepad.
8. When the file opens, delete all the entries in the Hosts file, except for the following line: 127.0.0.1 localhost
9. Close Notepad and save your changes when prompted.
Windows XP
1. Click Start > Search.
2. Click All files and folders.
3. In the "All or part of the file name" box, type: hosts
4. Verify that "Look in" is set to "Local Hard Drives" or to (C:).
5. Click More advanced options.
6. Check Search system folders.
7. Check Search subfolders.
8. Click Search.
9. Click Find Now or Search Now.
10. For each Hosts file that you find, right-click the file, and then click Open With.
11. Deselect the "Always use this program to open this program" check box.
12. Scroll through the list of programs and double-click Notepad.
13. When the file opens, delete all the entries in the Hosts file except for the following line: 127.0.0.1 localhost
14. Close Notepad and save your changes when prompted.