It may be that I have misunderstood the way you wish to have avast installed.

However, I just removed avast from my system and then re-installed the current release (4.7.892) onto a partition on a different drive from the C: drive.

I have no errors reported during the installation or during a few restarts since the install and avast is working as usual.

This is also been the long term configuration for avast of one of the folks I support. I just confirmed that no problems have been experienced with avast on that system.

Both the systems mentioned here are WinXP SP2.