Can you try deleting the file <avast>\setup\reboot.txt and see if it resolves the problem?
If it does not, please post ~100 lines from the END of the file <avast>\setup\setup.log
Thanks
Vlk
Erasing reboot.txt didn't works so here are the lines you ask for:
\ash2F.tmp", """""""""""""""""""""""""""""""""""""""""""""""\ashSimpl.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\ash30.tmp", """""""""""""""""""""""""""""""""""""""""""""""\ashSkPcc.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\ash31.tmp", """""""""""""""""""""""""""""""""""""""""""""""\ashSkPck.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\ash32.tmp", """""""""""""""""""""""""""""""""""""""""""""""\ashUpd.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\ash33.tmp", """""""""""""""""""""""""""""""""""""""""""""""\ashWebSv.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\asw34.tmp", """""""""""""""""""""""""""""""""""""""""""""""\aswUpdSv.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\sch35.tmp", """""""""""""""""""""""""""""""""""""""""""""""\sched.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\Vis36.tmp", """""""""""""""""""""""""""""""""""""""""""""""\VisthAux.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\Vis37.tmp", """""""""""""""""""""""""""""""""""""""""""""""\VisthLic.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\Vis38.tmp", """""""""""""""""""""""""""""""""""""""""""""""\VisthUpd.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\SPANISH\Bas39.tmp", """""""""""""""""""""""""""""""""""""""""""""""""""""""\Base.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\SPANISH\Lan3A.tmp", """""""""""""""""""""""""""""""""""""""""""""""""""""""\Lang.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\AhA3B.tmp", """""""""""""""""""""""""""""""""""""""""""""""\AhAScr.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\AhJ3C.tmp", """""""""""""""""""""""""""""""""""""""""""""""\AhJsctNs.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\AhR3D.tmp", """""""""""""""""""""""""""""""""""""""""""""""\AhResJs.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\AhR3E.tmp", """""""""""""""""""""""""""""""""""""""""""""""\AhRuiJs.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\ash3F.tmp", """""""""""""""""""""""""""""""""""""""""""""""\ashCmd.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\ash40.tmp", """""""""""""""""""""""""""""""""""""""""""""""\ashEnhcd.exe)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\asw41.tmp", """""""""""""""""""""""""""""""""""""""""""""""\aswCmnB.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\asw42.tmp", """""""""""""""""""""""""""""""""""""""""""""""\aswCmnOS.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\asw43.tmp", """""""""""""""""""""""""""""""""""""""""""""""\aswCmnS.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\asw44.tmp", """""""""""""""""""""""""""""""""""""""""""""""\aswEngin.dll)
12:08:02 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\asw45.tmp", """""""""""""""""""""""""""""""""""""""""""""""\aswScan.dll)
12:08:02 min/gen Return code: 0x20000000 [Something done]
12:08:02 min/gen Stopped: 01.05.2007, 12:08:02
12:08:02 min/gen Started: 01.05.2007, 12:08:02
12:08:02 min/gen Running setup_av_pro-3e9 (1001)
12:08:02 nrm/sys Operating system: WindowsXP ver 5.1, build 2600, sp 2.0 [Service Pack 2]
12:08:02 vrb/sys Computer WinName: JOLLY-E896C5927
12:08:03 min/sys Windows Net User: JOLLY-E896C5927\mat77
12:08:03 min/gen Cmdline: /stopstat /silent /noreboot
12:08:03 vrb/gen Operation set to INST_OP_[16]
12:08:03 min/gen Old version: 3e9 (1001)
12:08:03 nrm/gen SGW32P::CheckIfInstalled set m_bAlreadyInstalled to 1
12:08:03 nrm/int SYNCER: Type: use IE settings
12:08:03 nrm/int SYNCER: Auth: another authentication, use WinInet
12:08:03 vrb/pkg Part prg_av_pro-3e9 is installed
12:08:03 vrb/pkg Part vps-73702 is installed
12:08:03 vrb/pkg Part news-4b is installed
12:08:03 vrb/pkg Part setup_av_pro-3e9 is installed
12:08:03 vrb/pkg Part jrog-3 is installed
12:08:03 min/gen Old version: 3e9 (1001)
12:08:07 nrm/pkg Transferred files: 0
12:08:07 nrm/pkg Transferred bytes: 0
12:08:07 nrm/pkg Transfer time: 0 ms
12:08:07 vrb/fil NeedReboot=false
12:08:07 vrb/sys Reboot set by filRenameOnReboot(C:\Archivos de programa\Alwil Software\Avast4\Setup\reboot.txt,)
12:08:07 vrb/fil MoveFileEx("C:\Archivos de programa\Alwil Software\Avast4\Setup\reboot.txt", NULL)
12:08:07 min/gen Return code: 0x20000001 [Nothing done]
12:08:07 min/gen Stopped: 01.05.2007, 12:08:07
Hope you can work this out :'(