No second harddrive after w2ksp4 (again)

After updating win200 pro en from sp3+hotfixes to sp4 i could not see my
second harddrive.
This happend to me after a previous service pack too.
I can not remember, which file has to be downgraded to the previous version.

Please help to find the affected file (ide harddrive).

Please answer by email also, because i do not read this newsgroup regulary.

Regards,
Uwe