Important steps when cleaning virus

When you are putting scan for viruses you have to disable system restore. Windows XP backups your system at times, so that you can revert back to the working condition if your system is not working after installing X software. You can select the restore point before that day you installed that X software, so your system can work normally.

If your system has a virus, your windows might unknowingly already backed up the virus with other files. Your Anti Virus software can not remove virus from these backed up files because windows is protecting them. So, after your Anti Virus scans and cleans rest of the system, the virus can start spreading again from those backed up files.

So, first turn off the system restore in all drives before starting the scanning. You can do this by going to system properties(either through control panel, or by right clicking on My Computer icon). Then go to System Restore > Turn Off. You can hit the Win + Pause on the keyboard to bring up the System Properties.

And every time scan your system by booting into safe mode because when started in safe mode, windows loads minimal files to start the system.