it's quite strange... I have taken cscapi.dll from a non-vlited Business Vista (i don't have original DVD because my version is licensed MSDN-AA so the data files are in my university site...and I have to download Windows AIK) and in the Details, it says Offline Files Win32 API. I have removed with vLite Offline Files feature and in my installation, there isn't it. at first, I have tried to create a dummy cscapi.dll in windows\system32 folder and I started again the installation. it said the cscapi.dll is invalid...so it's looking for it. Probably, I have select too many option, lol... However I have add the file but the installation doesn't complete because it seems to require Terminal Service by looking in Event Register. I'll try to integrate this service manually and I'll try again the installation.