Ok i solved the problem in my PC

the error was in regedit:
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[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Mozilla Firefox (1.5)]
"DisplayName"="Mozilla Firefox (1.5)"
"UninstallString"="C:\\Programmi\\Mozilla Firefox\\uninstall\\uninstall.exe /ua \"1.5 (it)\""
"DisplayIcon"="C:\\Programmi\\Mozilla Firefox\\firefox.exe,0"
"DisplayVersion"="1.5 (it)"
"Comment"="Mozilla Firefox"
"InstallLocation"="C:\\Programmi\\Mozilla Firefox"
"NoModify"=hex(4):
"NoRepair"=hex(4):
"Publisher"="Mozilla"
"URLInfoAbout"="
http://www.mozilla.org/"
"URLUpdateInfo"="
http://www.mozilla.org/products/firefox/"
------------------------------------------------------------------------------------------------
In the values "NoModify" and "NoRepair".
I saw in these values: "(Valore DWORD non valido)", in english something like "(DWORD value not valid)" and I solved deleting these 2 keys.
Probably with a regedit checker you could find these errors (I tried ccleaner but it didn't find), but I found them manually with the "Ignore List" in Zsoft Uninstaller.
I think you can find these errors exporting all key, like HKLM, opening this with a editor e finding the string "hex(4)". it shound be an error.
Byez and sorry for my english
