If you need a free antivirus program, perhaps you should try using Microsoft Security Essentials, which is available for Windows XP, Vista, and Windows 7.
When you go to download Microsoft Security Essentials, you have the option to download a 32 or 64 bit version. If you are unsure of the version of Windows you’re running, there is a Microsoft Support article that you can view.
After you’ve downloaded and installed Microsoft Security Essentials, you should make sure that you have the latest antivirus definitions.
When you launch the program, you should see four tabs: Home, Update, History, and Settings.
On the Home tab, you have the option to run a Quick, Full, or custom scan of your computer. You can also see if you have the latest virus and spyware definitions, as well as if you have real time protection enabled. Also, you can see when your next scan will be and you can also change your scan schedule.
On the Updates page, you can see see whether your antivirus and antispyware definitions are up to date, as well as update your definitions. You can also see when your definitions were created, your virus definition version, and your system definition version.
The History tab allows you to see detected items, what alert level they have, the date they were detected, and what action you took against the item. You can also view quarantined items, as well as allowed items.
The Settings tab enables you to view and change your scan schedule, check your default settings, view and change your real time protection settings, add and remove excluded files and locations, as well as file types and processes. You can also view and change advanced settings, such as scanning archive files, in addition to removable drives. You can also choose to create a System Restore point before your computer is scanned, and whether or not all users are allowed to view the history of detected files.
If you would like to try using Microsoft Security Essentials, you can download it for free from the Microsoft Security Essentials website.