XP Professional x64 - Installof Avast 4 fails

I wonder if someone can help.

I have just downloaded Avast 4 and tries to install on my XP Professional x64 which is a VMware session on my Mac.

When I double-click the setup .exe it stay up for a few seconds and then just disappears!

Has anyone experienced this or does anyone know what the problem is?

Thanks
Manish