Dear Plamen,
I got another Win7 machine where I was able to load hive from the mapped "X:" drive. I killed all related entries for the PERCH700 RAID controller and deleted the drivers as well.
Still blue screen upon booting, so I give up.
Many thanks for your and others comprehensive support in this topic. I can confirm, that Raid controllr under Windows 2003 Server R2 is not an option to convert this way.
Have a nice weekend.
Regards,
Pal