Can't D/L Updates

I have just reinstalled XP pro on a Dell Latitude D820 Laptop, and one of the first things I try to get done it to have an up-to-date anti-virus in place. I managed to find the drivers for the WLAN card, and can browse the internet successfuly, but I can’t seem to get Avast to auto-download its updates. I’m not sure if this issue is entirely to do with Avast, as I also can’t get AdAware to auto-update.
So not strictly an Avast problem, but if anyone can suggest some setting to change, I’d be quite appreciative.

First of all you cannot just simple reinstall Windows. You must format the drive then install Windows. Secondly you should install ALL necessary drivers and Windows Updates. Once all your drivers and Windows Updates are done then install all your old software and virus protection. Which version of Avast are you using? Did you install SP2 and SP3?

i need help my avast wont update the virus definition even manually

have you tried avast repair ?

For a repair of avast.
Windows, Add Remove programs, select ‘avast! Anti-Virus,’ click the Change/Remove button from the pop-up window, scroll down to Repair, click next and follow.