Internal structure of a registry file?

Hi folks,

is there any information available about the internal structure of a
registry file (e.g. \windows\system32\config\system)?
Background: I'll try to extract some data from a corrupt registry file
(after windows bluescreen), that even can't be opened with regedt32
any more. Are there tools that can open such a defective file and read
some data out??
Or any information about the file format?
Any idea is welcome!!
Thanx,

Chris