Most probably, the drivers of the NTFSPRO are ‘eating’ all available memory.
We must find a workaround…
avast does not have a rescue floppy. Maybe you can install AVG in another computer and create the rescue disks. Alwil Company works with BART CD that is another standalone product (not free).
I think the best is try to install Windows XP over your ‘old’ installation, I mean, choose the ‘Repair’ installation (or update an existing installation). You won’t lose your programs settings, files, etc…
You could only lose Windows Updates already installed.
Better if you can do this with a XP+SP2 streamed CD.