BSOD during Avast scan in boot mode Windows XP SP3

[ahhnoo]

I have used avast home edition for almost five years. Great program, no problems until possibly now. I have Windows XP SP3. And I usually do a boot scan with avast once a week. However, since December 3, 2008, everytime I thorough scan with avast inside boot mode, it progresses but before it ends around 50% the computer crashes and I get a Blue Screen of Death. The BSOD has the following:

kernel_stack_inpage_error

*** Stop: 0x00000077
0xC000009C
0xC000009c
0x00000000
0x010FE000

Yet, I have had no virus alerts or infections for over a year. However, I am able to do a thorough scan in Regular Mode. There is no notice of infection. I do not think it is infected, but I have no idea why this is happening. I am computer illiterate. This is my only computer, and I cannot afford another one at this time. Help is greatly appreciated.

[Lisandro]

Never post twice the same... just double the effort of help :'(
Follow http://forum.avast.com/index.php?topic=40668.new#new

[Lisandro]

2. If there is no virus, uninstall the home edition and install the professional edition.

Of avast? This is not necessary (the user does not ought to do it). The Home version works perfectly.