How To Write A VxD?

Does anyone know how to write a VxD, or where there is information on it? As I only have something small but specific in mind for the moment (I want to toggle RTS in the COM ports manually, rather than use the built-in Windows functions which are too slow), I don't want to spend an horrific amount of money on some software to help me write it (WinDriver sounded great, but they want $1200 for a licence to go on '95/'98 AND NT! - I don't think so).

What is the best (but most cost-effective) tool or software package to write a VxD with? Where can I get details of how to do it?

The first option I would consider is the MS DDK. This is free I believe but
typically has an enormous learning curve also. It's a fairly large download
but comes with the MSDN CDs. Another option is WinRT from Blue Water
Systems (www.bluewatersystems.com). I think it costs a bit less than $1200.
They have fairly good samples also.

Thankyou for your reply. I'm afraid the WinRT, like WinDriver, is a no-go; it only cost marginally less than $1200, and for a one-off driver it is not worth it. For people writing drivers on a constant basis it would probably be OK, but not for me.

I already have the DDK, but knowing where to start is the difficult bit. Got any ideas?

I agree, getting started with the DDK can be difficult.
I would approach it like I do most things, check out samples.
As many as you can get your hands on until you have at least
some clue about how to get started with what you need to do.
Sorry I can't be more helpful but there are others around here
who have DDK experience that can probably help with specific
questions.

OK, thankyou for your help. I will dig deeply...