does formatting a usb disk make it secure for future use ?

Completely wiping and reinstalling the OS should remove everything.

I am going to borrow our quietman7's reply to reformatting as he covers a lot.

Caution: If you are considering backing up data and reformatting, keep in mind, with a Virut infection, there is always a chance of backed up data reinfecting your system. If the data is that important to you, then you can try to salvage some of it but there is no guarantee so be forewarned that you may have to start over again afterwards if reinfected by attempting to recover your data. Only back up your important documents, personal data files, photos to a CD or DVD drive, not a flash drive or external hard drive as they may become compromised in the process. The safest practice is not to backup any executable files (*.exe), screensavers (*.scr), autorun (.ini) or script files (.php, .asp, .htm, .html, .xml ) files because they may be infected by malware. Avoid backing up compressed files (.zip, .cab, .rar) that have executables inside them as some types of malware can penetrate compressed files and infect the .exe files within them. Other types of malware may even disguise itself by hiding a file extension or adding to the existing extension as shown here (click Figure 1 to enlarge) so be sure you look closely at the full file name. If you cannot see the file extension, you may need to reconfigure Windows to show file name extensions. Then make sure you scan the backed up data with your anti-virus prior to to copying it back to your hard drive.

If your CD/DVD drive is unusable, another word of caution if you are considering backing up to an external usb hard drive as your only alternative. External drives are more susceptible to infection and can become compromised in the process of backing up data. I'm not saying you should not try using such devices but I want to make you aware of all your options and associated risks so you can make an informed decision if its worth that risk.

Again, do not back up any files with the following file extensions: exe, .scr, .ini, .htm, .html, .php, .asp, .xml, .zip, .rar, .cab as they may be infected.

If you're not sure how to reformat or need help with reformatting, please review:

These links include step-by-step instructions with screenshots:

Vista users can refer to these instructions:

Don't forget you will have to go to Microsoft Update and apply all Windows security patches after reformatting.

Note: If you're using an IBM, Sony, HP, Compaq or Dell machine, you may not have an original XP CD Disk. By policy Microsoft no longer allows OEM manufactures to include the original Windows XP CD-ROM on computers sold with Windows preinstalled. Instead, most computers manufactured and sold by OEM vendors come with a vendor-specific Recovery Disk or Recovery Partition for performing a clean "factory restore" that will reformat your hard drive, remove all data and restore the computer to the state it was in when you first purchased it. See Technology Advisory Recovery Media. If the recovery partition has become infected, you will need to contact the manufacturer, explain what happened and ask them to send full recovery disks to use instead..

If you need additional assistance with reformatting or partitioning, you can start a new topic in the Operating Systems Subforums forum.

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