Avast was installed and operating correctly for several years. After upgrading the AMD processor from a 2 core Athlon 64 X2 5600 (driver AMDK8.sys) to a 4 core Phenom II X4 945 (driver AMDPPM64.sys) ...
The system boots to the point of entering the GUI and freezes with a working (moveable) mouse pointer on a black screen. Disk activity continues for more than 30 seconds, becomes infrequent, and eventually stops. Enabling boot logging and examining the log in safe mode shows FastFat.sys as the last driver loaded. That driver is part of the file system, version 5.2.3790.3959 (srv03_sp2_rtm.070216-1710) 2-16-2006 247,808 bytes. Extract copy from SP2 CD and byte compare - files are identical. In this case, the last driver loaded appears to be the victim, not the assassin.
Booting to Safe Mode and removing Avast resolved the problem completely. After restarting, in normal mode, restarted in Safe Mode and ran the AvastClear cleanup tool. Restarted in Normal mode.
Found several Avast files and device driver entries were NOT removed by either the uninstall or the cleanup tool (see below) and removed them manually. Used the device manager to show hidden devices and removed 5 legacy device drivers beginning asw... the driver file no longer existed for any of these. Also removed 2 device driver entries for AMD Athlon 64 X2 5600 Processor, leaving 4 for the Phenom II 945.
Restarted system in normal mode. Installed Avast 2015 successfully until system restart. Same hang at GUI start with black screen and mouse cursor. Restarted in Safe mode, uninstalled Avast, system starts normally. Re-checked boot logs, Fastfat.SYS
At this point I don't see any obvious path to resolve Avast hanging with a 4 core CPU under XP x64. The only hardware change was the processor chip, and the software issues are described above. Its as if Avast has an (invalid) implicit assumption that an XP x64 system doesn't support more than 2 CPU cores.
Any suggestions? [A suggestion to wipe the drive and make a "clean" install of the OS two SPs and several hundred security updates will be deferred until the next aqueous solid phase transition in the infernal region. A later version of the Windows OS will also be installed at that time on a second drive (the BIOS has a multi-boot menu). Any other suggestions...? ]
---------------------------------------------
[Avast files found after uninstall and cleanup tool]
files found in \windows\system32 and removed
aswBoot.exe
files found in \windows\system32\drivers and removed
aswrdr.sys.1400446869312
aswsnx.sys.1400446869312
files found in \windows\prefetch and removed
ASWOFFERTOOL.EXE-0292D192.pf
ASWOFFERTOOL.EXE-074176E1.pf
ASWOFFERTOOL.EXE-0DCB1C11.pf
ASWOFFERTOOL.EXE-21A97491.pf
ASWRUNDLL.EXE-2BD6D5AD.pf
ASWWRCIELOADER32.EXE-08C9EDC8.pf
ASWWRCIELOADER64.EXE-2449928F.pf
AVAST_FREE_ANTIVIRUS_SETUP 20-32EFE1EE.pf
AVAST_FREE_ANTIVIRUS_SETUP.EX-042AC44B.pf
AVASTEMUPDATE.EXE-270AFBBD.pf
AVASTSVC.EXE-03B6BADE.pf
AVASTUI.EXE-0DFF7A0C.pf
AVASTUI.EXE-361EA49B.pf
...these files and folder found in \windows\WinSxs and subdirectories were NOT removed
amd64_policy.11.0.avast.vc110.crt_2036b14a11e83e4a_x-ww_f68d43d1\11.0.60610.1.cat
amd64_policy.11.0.avast.vc110.crt_2036b14a11e83e4a_x-ww_f68d43d1\11.0.60610.1.policy
x86_policy.11.0.avast.vc110.crt_2036b14a11e83e4a_x-ww_96cea1b1\11.0.60610.1.cat
x86_policy.11.0.avast.vc110.crt_2036b14a11e83e4a_x-ww_96cea1b1\11.0.60610.1.policy
amd64_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_188c14c2.cat
amd64_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_188c14c2.manifest
x86_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_e6822ee2.cat
x86_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_e6822ee2.manifest
amd64_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_188c14c2\atl110.dll
amd64_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_188c14c2\mfc110u.dll
amd64_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_188c14c2\msvcp110.dll
amd64_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_188c14c2\msvcr110.dll
x86_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_e6822ee2\atl110.dll
x86_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_e6822ee2\mfc110u.dll
x86_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_e6822ee2\msvcp110.dll
x86_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_e6822ee2\msvcr110.dll
amd64_policy.11.0.avast.vc110.crt_2036b14a11e83e4a_x-ww_f68d43d1
x86_policy.11.0.avast.vc110.crt_2036b14a11e83e4a_x-ww_96cea1b1
amd64_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_188c14c2
x86_avast.vc110.crt_2036b14a11e83e4a_11.0.60610.1_x-ww_e6822ee2
_avast_
