system restore on ubuntu

I use ubuntu 8. Recently as I was updating avast antivirus (for linux), the process simply vanished. Updating the definitions was always a smooth process but on this day, it simply disappeared after 80%. The program was installed Accessories, but when i tried to uninstall it using "Add/Remove" option, Avast was nowhere to be found. This application has gone corrupt or something like that. Anyway I downloaded the deb file afresh from the avast site and reinstalled it. Installation went ahead smoothly. Yet, there is no trace of this application. Once again, it is not found in "Add/Remove" and clicking on the shortcut gives an error An error occured in Avast! engine: invalid code

I have messed big way, how can I get it back to the stage it was two days ago....something similar to windows system restore.

Or else can anyone suggest how to about this issue....I have no idea about linux.

Check for avast in Synaptic package manager(System > Administration > Synaptic Package Manager) first and if you find it there, try uninstall it and reinstall if you like . I think there is no need to have an antivirus for ubuntu

Thanks, I found it in synaptic manager and successfully uninstalled it. Then I reinstalled it from freshly downloaded deb file from avast website. Installation was said to be successful. No icons or shortcuts were generated and trying to launch application only gives error.

Note: I use antivirus in ubuntu to scan for viruses in pen drives before using them on windows computer.