Vista - Loading Registry hive with PowerShell

Hello,

how can I load and unload a Registry hive with PowerShell?
Of course, I could call reg.exe to load and unload my hive, but this
seems not very beautiful for me. Further, there are different versions
of reg.exe which have a different parameter ordering.
I´m trying to modify the Default User´s ntuser.dat with PowerShell.
Can anybody give some hints? Please bear with me, I´m just starting to
use PowerShell...

Thanks for your reply!
Andi