Hello everyone! I have to ask some questions about how to program device driver programs. I saw many examples here but I don't understand much of them.. I have some questions here hope someone will reply and sorry for dumb questions..
#1 How does Device Driver work ?
#2 How to run .SYS file ?
#3 Can someone write kernel mode driver that will just pop up MessageBox when loaded and how to load it ?
#4 Simple code if possible.
I'm just interested whats difference between kernel mode and user mode ? Why kernel mode drivers can't be removed from usermode ? Just some examples please. Thanks.

Overflowz,

Those questions aren't outright dumb, yet you have to understand that explanation requires you to know some basics. Have you read some books about Windows architecture already? "Windows Internals", "Inside Microsoft Windows", anything about Windows I/O model?

Some short answers:
#1: Quite efficiently.
#2: It is supposed to be loaded by OS.
#3: Someone can, what you will do with all those driver/device objects, IRPs and such in that source?
#4: I wish I can fly with a simple device (with simple driver, with simple code) too.

If you're really interested, there are tutorials, articles and kits.

Should I read those books first ?

Overflowz,

Four-F wrote good series of articles at wasm.ru about this. While those books aren't absolute necessity, you may find them informative.

Try http://www.osronline.com/ as well as Four-F series (very good).

Okay thanks. I'll read that

to run driver you have 2 choices
- let it to be loaded at boot (loaded through registry key)
- load it on demand (requires calling only about 5 APIs, surely not more than 10, requires also admin privileges) - download samples from FASM download section, also scan forum for some samples if it should be for 32 bit