Problem installing Avisynth

When installing Avisynth 2.56 or 2.56a (WinXP SP2, Russian) I get error message 'Couldn't write to registry' at about 10-15% of progress bar. The installer stops after creating plugin folder with 2 dll's and a .avsi file inside and writes to registry values for folders location in Avisynth entry. As I can guess some system entries are touched during installation but have no idea which ones to check for read/write permissions (I have admin rights on my PC).
Also tried disabling Norton 2005 real-time protection (useless). What other applications can be in conflict (there were no older Avisynth installations, no DVDRebuilder etc.)? Any ideas please? Thanks.

do you have admin privileges in your system, i.e, can you modify or create registry keys ?

did you tried to setup in Safe Mode ? restart the system ?

Might also want to check the permissions for the registry keys in question.

Which from a look at the NSIS script would be:
HKLM\SOFTWARE\AviSynth
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uni nstall\AviSynth
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uni nstall\AviSynth
HKLM\SOFTWARE\Classes\.avs
HKCR\.avs
HKCR\CLSID\{E6D6B700-124D-11D4-86F3-DB80AFD98778}
HKCR\avifile\Extensions\avs
HKCR\Media Type\Extensions\.avs
HKCR\avsfile

Thank you all for the useful info. I suspected there was something wrong with the installer 'cause it's very rare when I can't install something. I'll try the newer version first.
Alexander

V.2.57RC1 got installed without a problem, thanks again for your help.
Alexander