Ok well it worked! I had to take the Ntfs drive out of my mother in laws computer(the one with the problem) and put it into my system(xp also) as a slave.
Doing that gave me complete control of the files and such. i renamed the file in the C:\Program Files\Awilla\Avast folder from AswBoot.exe to BadAswBoot.exe.
And also while i was there i also had avast scan the drive for the virus i was trying to get rid of. it found it and deleted it.
So then i put the drive back into my Mother in laws case and restarted it. As i had said previously i had tried to repair the installation of xp, but when it had restarted it went back to scan, well it went ahead and finished the repair (which took 40 mins) and when it was done it rebooted.
At first it looked as if the Avast was going to start its boot scan again but then it said error and then continued with the boot up into windows! Finally i had her desktop back!
so i had to reinstall all of the updates and such.
but i was happy that i finally had it fixed!
The only suggestion i have is PLEASE take off the option to scan at boot time (or at least make it harder to find) until the problem with the scan at boot time is more compatable with the usb keyboards.
or another suggestion is to just have the boot scan automatically take any found virus's directly to the quaranteen area so there is no longer any need for key input at that stage. then the found items could be dealt with after boot up.
any way just a couple of ideas for you all. I thank you for all your help and I hope that maybe i can return the favor!
Thanks again!