To fix this error

Receptor RC:  REGDB_E_CLASSNOTREG (0x80040154)

creating new VMs in Sun VirtualBox you have to follow this steps:

We don't know yet what causes this, but it's an installation error that
happens on some Vista systems. To fix it:

1) Open a standard command line (not as administrator)

2) "cd C:\Program Files\Sun\VirtualBox"

3) Issue "VBoxSVC /ReRegServer"

4) Issue regsvr32 VBoxC.dll

Then it will work.

 

Source:

http://vbox.innotek.de/pipermail/vbox-users/2007-January/000045.html