IIS 4 ATL DLL just won't register

Hi, I feel dumb as a box of hammers here.

Situation is that I've just started with this ATL COM Server Side Objects stuff on NT after 22 years of C/UNIX. I have a server running NT4+SP4/Site Server 3/P&M and IIS4. My Dev box has VC++ 6.0. I create a simple ATL DLL with just a couple of minor functions and copy it to the server. Regsvr32 it, and my ASP pages see it. Cool. Erm.. Until I try to recreate that DLL. I've tried **ALL** combinations of shutting down services(IIS/SS & Others), rebooting and regsvr32 -u the darn thing with no result. I simply get that 'In use' message whenever I try to overwrite it or DEL it.

I just know that this may sound obvious to many of you, but I'm an experienced C/C++ programmer but in a new and violent environment(NT) and I really need to solve this.

Any ideas anybody?

Kimbo