below is the hjt log file before AVASt installation (all working fine):

Logfile of HijackThis v1.98.2
Scan saved at 21:38:27, on 24/01/2005
Platform: Windows XP SP1 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP1 (6.00.2800.1106)

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\System32\ctfmon.exe
C:\WINDOWS\system32\spoolsv.exe
C:\WINDOWS\System32\wuauclt.exe
C:\WINDOWS\System32\wpabaln.exe
C:\Program Files\Internet Explorer\iexplore.exe
C:\Documents and Settings\Owner\My Documents\New Folder\HijackThis.exe

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Page = http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.microsoft.com/isapi/redir.dll?prd={SUB_PRD}&clcid={SUB_CLSID}&pver={SUB_PVER}&ar=home
R1 - HKCU\Software\Microsoft\Internet Connection Wizard,ShellNext = http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome
O3 - Toolbar: &Radio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINDOWS\System32\msdxm.ocx
O4 - HKCU..\Run: [CTFMON.EXE] C:\WINDOWS\System32\ctfmon.exe
O9 - Extra button: Related - {c95fe080-8f5d-11d2-a20b-00aa003c157a} - C:\WINDOWS\web\related.htm
O9 - Extra ‘Tools’ menuitem: Show &Related Links - {c95fe080-8f5d-11d2-a20b-00aa003c157a} - C:\WINDOWS\web\related.htm
O17 - HKLM\System\CCS\Services\Tcpip..{854FBA0D-1117-4818-9F1B-20D5C7FC7E4B}:

now is the hjt log file after AVASt installation and before restart computer (all still working fine):

Logfile of HijackThis v1.98.2
Scan saved at 21:50:19, on 24/01/2005
Platform: Windows XP SP1 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP1 (6.00.2800.1106)

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\System32\ctfmon.exe
C:\WINDOWS\system32\spoolsv.exe
C:\WINDOWS\System32\wuauclt.exe
C:\WINDOWS\System32\wpabaln.exe
C:\Documents and Settings\Owner\My Documents\New Folder\HijackThis.exe

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Page = http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.microsoft.com/isapi/redir.dll?prd={SUB_PRD}&clcid={SUB_CLSID}&pver={SUB_PVER}&ar=home
R1 - HKCU\Software\Microsoft\Internet Connection Wizard,ShellNext = http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome
O3 - Toolbar: &Radio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINDOWS\System32\msdxm.ocx
O4 - HKLM..\Run: [avast!] C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
O4 - HKCU..\Run: [CTFMON.EXE] C:\WINDOWS\System32\ctfmon.exe
O9 - Extra button: Related - {c95fe080-8f5d-11d2-a20b-00aa003c157a} - C:\WINDOWS\web\related.htm
O9 - Extra ‘Tools’ menuitem: Show &Related Links - {c95fe080-8f5d-11d2-a20b-00aa003c157a} - C:\WINDOWS\web\related.htm
O17 - HKLM\System\CCS\Services\Tcpip..{854FBA0D-1117-4818-9F1B-20D5C7FC7E4B}: NameServer = 192.168.1.1

in the end, below is the hjt log file after restart computer (all going wrong now):

Logfile of HijackThis v1.98.2
Scan saved at 21:59:34, on 24/01/2005
Platform: Windows XP SP1 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP1 (6.00.2800.1106)

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\Explorer.EXE
C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
C:\WINDOWS\System32\ctfmon.exe
C:\WINDOWS\system32\spoolsv.exe
C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
C:\Program Files\Alwil Software\Avast4\ashServ.exe
C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe
C:\WINDOWS\System32\wuauclt.exe
C:\WINDOWS\System32\wpabaln.exe
C:\WINDOWS\System32\cmd.exe
C:\Documents and Settings\Owner\My Documents\New Folder\HijackThis.exe

O3 - Toolbar: &Radio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINDOWS\System32\msdxm.ocx
O4 - HKLM..\Run: [avast!] C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
O4 - HKCU..\Run: [CTFMON.EXE] C:\WINDOWS\System32\ctfmon.exe
O9 - Extra button: Related - {c95fe080-8f5d-11d2-a20b-00aa003c157a} - C:\WINDOWS\web\related.htm
O9 - Extra ‘Tools’ menuitem: Show &Related Links - {c95fe080-8f5d-11d2-a20b-00aa003c157a} - C:\WINDOWS\web\related.htm
O17 - HKLM\System\CCS\Services\Tcpip..{854FBA0D-1117-4818-9F1B-20D5C7FC7E4B}: NameServer = 192.168.1.1