Hí Bilou, thanks a lot for the advise I've right chosen the described svcpack.inf method to get rid of the awful extracting of the .cat files. However, after numerous attempts it seems that I have success: I 've changed the extension of the names of the hotfix files into lowercase (e.g. KB873339.EXE to KB873339.exe) in svcpack.inf and in the SVCPACK folder and all hotfixes install fine. Btw I find better to use the /U switch instead of /O because one can see the very time consuming processes at T-13. I know, this sounds crazy but this was the only change I've made to the installation package and now it works. The forum is superb, I learn a lot - thank you again Andy