grazie menatwork.

nel frattempo aggiungo che, dopo averti inviato il log di hijack, è partito in automatico l'aggiornamento di firefox e, al completamento, mi sono ritrovata una pagina iniziale con un motore di ricerca mai visto prima e una toolbar altrettanto nuova. per questo, ti riposto il log di hijack qui, se dovesse servire.

ecco il log di avenger:

Logfile of The Avenger Version 2.0, (c) by Swandog46
http://swandog46.geekstogo.com

Platform: Windows XP

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Script file opened successfully.
Script file read successfully.

Backups directory opened successfully at C:\Avenger

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Beginning to process script file:

File "C:\Documents and Settings\Ivana\Impostazioni locali\Dati applicazioni\ServUpdater\ServiceUpd.exe" deleted successfully.

Error: file "C:\Programmi\Yontoo\YontooIEClient.dll" not found!
Deletion of file "C:\Programmi\Yontoo\YontooIEClient.dll" failed!
Status: 0xc0000034 (STATUS_OBJECT_NAME_NOT_FOUND)
--> the object does not exist

File "C:\Documents and Settings\All Users\Documenti\AppData\PoApp\PLauncher.exe" deleted successfully.

Error: file "folder to delete:" not found!
Deletion of file "folder to delete:" failed!
Status: 0xc0000034 (STATUS_OBJECT_NAME_NOT_FOUND)
--> the object does not exist


Error: "C:\Documents and Settings\Ivana\Impostazioni locali\Dati applicazioni\ServUpdater" is a folder, not a file!
Deletion of file "C:\Documents and Settings\Ivana\Impostazioni locali\Dati applicazioni\ServUpdater" failed!
Status: 0xc00000ba (STATUS_FILE_IS_A_DIRECTORY)
--> use "Folders to delete:" instead of "Files to delete:" to delete a directory


Error: "C:\Programmi\Yontoo" is a folder, not a file!
Deletion of file "C:\Programmi\Yontoo" failed!
Status: 0xc00000ba (STATUS_FILE_IS_A_DIRECTORY)
--> use "Folders to delete:" instead of "Files to delete:" to delete a directory


Error: "C:\Documents and Settings\All Users\Documenti\AppData\PoApp" is a folder, not a file!
Deletion of file "C:\Documents and Settings\All Users\Documenti\AppData\PoApp" failed!
Status: 0xc00000ba (STATUS_FILE_IS_A_DIRECTORY)
--> use "Folders to delete:" instead of "Files to delete:" to delete a directory


Completed script processing.

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Finished! Terminate.