FSD disables driver a:

Hi there ,

I have an NT 4 FSD which works fine except that it disables drive A:
When I made the FSD loadable automatically (start =2 ) I noticed that
dirve A: is disabled already after
DriverEntry() routine is called . All I am doing in driver Entry is :
IoCretaeDevice () , IoCreateSymbolicLink()
and IoRegisterFileSystem() (which is a void function) . If I drop the last
call , A: is not disabled .

Any Idea why this is happening ?

Dubi