Being an Avast user and reading your comments, I decide to give AntiVir a try.
After several attempts to download the W98 version at last one site responded and downloaded.

The AntiVir installed OK (after uninstalling Avast from Ctrl Panel) and it immediately went for an update. Unfortunately despite asking my firewall (Sygate) to always allow access the update never started. I asked it to abort the download but the dialogue boxes refused to go away.
I rebooted and started to update again with identical results (except Sygate didn't ask for permission again). Again the update dialogue boxes persisted after an abort request.

I reinstalled AntiVir from a second download from another mirror site with the exact same result.

Avast is back on my m/c and needed no configuration as it remembered my previous settings to the letter.