YEAH! Just solved!!! Now it works... need to install anyway the ewf files.
I used the files extracted from "XPeSP2FeaturePack2007.iso" downloaded by MS site.
1. replace the original ntldr with renamed ewfntldr using recovery console on xp CD and restart
2. copy ewfapi.dll, ewfdll.dll, ewfmgr.exe in system32 dir
3. copy ewf.sys in system32\drivers dir
4. copy horm.dat in root dir (same as ntldr), c:\
5. add to the registry the ewf informations using a .reg file (ones indicated by sfiorito here:
http://mason.gmu.edu/~sfiorito/eXPinstall.htm)
6. enable hibernation support on the system if not yet
7. restart and use command prompt as following:
***
Microsoft Windows XP [Versione 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\Documents and Settings\Administrator>ewfmgr
RAM (REG) Configuration
Device Name "\Device\HarddiskVolume1" [C:]
HORM Active
***
If you see "HORM active" now you can try to hibernate and resume as many times you want by the same hiberfile.sys
EWF protection is still disabled till you don't enable it using ewfmgr.exe