A good offline antivirus

I do not have an internet connection. My operating system is Windows vista and have a RAM of 1GB. I need to know which antivirus is best suited for my use in such an offline environment and configuration. Please recommend me a good antivirus and is there any method to update the antivirus in an offline environment.

There is no good offline antivirus as such. As you are in an offline environment, you do not have threats from the web. All you have to be careful of are the external devices that you connect. Always scan whatever portables you insert. Place a scheduled scan that takes place at some particular time on a daily basis. So, you can install a setup of any recent antivirus and do the above mentioned processes.

According to me Avast antivirus is a good offline antivirus as it includes the feature of boot scan. Boot scan means a scan before windows can load. This means that it scans even before the virus execution can take place and removes the virus forcefully. This is the best feature an offline antivirus must have. Here below is the link provide for the setup of Avast antivirus.
DOWNLOAD

NOD32 is the best offline antivirus that is available. This is the only antivirus that provides the feature of offline updation. For updation, you have to follow the below given steps:

1. Make a directory known as "nod_upd".
2. Extract or copy the update files to this directory.
3. Next, write it to a CD/DVD and open NOD32 Control Center and select update.
4. Then, select SETUP button and in the "SERVER" drop-down, select CD/DVD-ROM drive as your updation option.
5. Now, insert the CD/DVD and select "UPDATE NOW".

Your computer is now updated.