Our system is affected by virus(Trojan) and Internet is not opening any page,yahoo or rediff etc?

we are using Win Xp Service Pack 2 and 150GB hard disks.the virus is in C: drive the antivirus of free edition is only cleaning .But i want to remove permanently with out formatting the c: drive because we have important data in it.Please Answer how to do.I have 2005 and 2006 orginal cds with me but it is not allowing to install the Norton 2005%262006.We didn't on the Fire wall for that reason i think the virus has attacked please mail me Asap.ThANK YOU

Our system is affected by virus(Trojan) and Internet is not opening any page,yahoo or rediff etc?trojan

Here is what you do!

1.Get an external hard drive.

2.Move everything you want to save on that external hard drive.

3.Reformat the entire hard drive.

4.Reinstall the operating system.

5.Resinstall all the apps.

6.DO NOT install McAfee or Norton, even if you have the full versions.

7.Get AVG. It is a much better antivirus and it is free.

http://free.grisoft.com/doc/1

8.For the firewall, use zonealarm. They have a free version too.

http://www.zonelabs.com/store/content/co...

9.Move your backups again.

10.Update and run the antivirus frequently.

11.Backup on a regular basis.

12.DO NOT forget the lesson you learned today.